diff --git a/Manifest.toml b/Manifest.toml
index ed687d0..d326f5f 100644
--- a/Manifest.toml
+++ b/Manifest.toml
@@ -2,7 +2,31 @@
 
 julia_version = "1.12.6"
 manifest_format = "2.0"
-project_hash = "ef9b3b10e57f337aaf073b0d40fa4372a1697b0e"
+project_hash = "3e47cb4426f8b430734383590f86ec8b7094cfd2"
+
+[[deps.Accessors]]
+deps = ["CompositionsBase", "ConstructionBase", "Dates", "InverseFunctions", "MacroTools"]
+git-tree-sha1 = "7063ad1083578215c7c4bf410368150abe8d5524"
+uuid = "7d9f7c33-5ae7-4f3b-8dc6-eff91059b697"
+version = "0.1.45"
+
+    [deps.Accessors.extensions]
+    AxisKeysExt = "AxisKeys"
+    IntervalSetsExt = "IntervalSets"
+    LinearAlgebraExt = "LinearAlgebra"
+    StaticArraysExt = "StaticArrays"
+    StructArraysExt = "StructArrays"
+    TestExt = "Test"
+    UnitfulExt = "Unitful"
+
+    [deps.Accessors.weakdeps]
+    AxisKeys = "94b1ba4f-4ee9-5380-92f1-94cde586c3c5"
+    IntervalSets = "8197267c-284f-5f27-9208-e0e47529a953"
+    LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
+    StaticArrays = "90137ffa-7385-5640-81b9-e52037218182"
+    StructArrays = "09ab397b-f2b6-538f-b94a-2f83cf4a842a"
+    Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
+    Unitful = "1986cc42-f94f-5a68-af5c-568840ba703d"
 
 [[deps.AliasTables]]
 deps = ["PtrArrays", "Random"]
@@ -51,6 +75,11 @@ git-tree-sha1 = "962834c22b66e32aa10f7611c08c8ca4e20749a9"
 uuid = "944b1d66-785c-5afd-91f1-9de20f533193"
 version = "0.7.8"
 
+[[deps.CommonSolve]]
+git-tree-sha1 = "99ee296f88c12485402e37c2fd025f95ae097637"
+uuid = "38540f10-b2f7-11e9-35d8-d573e4eb0ff2"
+version = "0.2.9"
+
 [[deps.Compat]]
 deps = ["TOML", "UUIDs"]
 git-tree-sha1 = "9d8a54ce4b17aa5bdce0ea5c34bc5e7c340d16ad"
@@ -71,6 +100,30 @@ deps = ["Artifacts", "Libdl"]
 uuid = "e66e0078-7015-5450-92f7-15fbd957f2ae"
 version = "1.3.0+1"
 
+[[deps.CompositionsBase]]
+git-tree-sha1 = "802bb88cd69dfd1509f6670416bd4434015693ad"
+uuid = "a33af91c-f02d-484b-be07-31d278c5ca2b"
+version = "0.1.2"
+weakdeps = ["InverseFunctions"]
+
+    [deps.CompositionsBase.extensions]
+    CompositionsBaseInverseFunctionsExt = "InverseFunctions"
+
+[[deps.ConstructionBase]]
+git-tree-sha1 = "b4b092499347b18a015186eae3042f72267106cb"
+uuid = "187b0558-2788-49d3-abe0-74a17ed4e7c9"
+version = "1.6.0"
+
+    [deps.ConstructionBase.extensions]
+    ConstructionBaseIntervalSetsExt = "IntervalSets"
+    ConstructionBaseLinearAlgebraExt = "LinearAlgebra"
+    ConstructionBaseStaticArraysExt = "StaticArrays"
+
+    [deps.ConstructionBase.weakdeps]
+    IntervalSets = "8197267c-284f-5f27-9208-e0e47529a953"
+    LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
+    StaticArrays = "90137ffa-7385-5640-81b9-e52037218182"
+
 [[deps.Crayons]]
 git-tree-sha1 = "249fe38abf76d48563e2f4556bebd215aa317e15"
 uuid = "a8cc5b0e-0ffa-5ad4-8c14-923d3ee1735f"
@@ -104,10 +157,10 @@ uuid = "ade2ca70-3891-5945-98fb-dc099432e06a"
 version = "1.11.0"
 
 [[deps.Distributions]]
-deps = ["AliasTables", "FillArrays", "LinearAlgebra", "PDMats", "Printf", "QuadGK", "Random", "SpecialFunctions", "Statistics", "StatsAPI", "StatsBase", "StatsFuns"]
-git-tree-sha1 = "3c8a0a9a6d4a10bdfb6b751bd2b6051ed3e25fd4"
+deps = ["AliasTables", "FillArrays", "LinearAlgebra", "PDMats", "Printf", "QuadGK", "Random", "Roots", "SpecialFunctions", "Statistics", "StatsAPI", "StatsBase", "StatsFuns"]
+git-tree-sha1 = "cd3c5ac74cd3923c8945c6a81518c46abd0e73a3"
 uuid = "31c24e10-a181-5473-b8eb-7969acd0382f"
-version = "0.25.127"
+version = "0.25.129"
 
     [deps.Distributions.extensions]
     DistributionsChainRulesCoreExt = "ChainRulesCore"
@@ -169,11 +222,11 @@ version = "1.11.0"
 
 [[deps.GeneralUtils]]
 deps = ["CSV", "DataFrames", "DataStructures", "Dates", "Distributions", "JSON", "NATS", "PrettyPrinting", "Random", "Revise", "SHA", "UUIDs"]
-git-tree-sha1 = "76d2628787838a67d6e8192e428991a7522883f0"
+git-tree-sha1 = "f1bad7621e6ac2d235adc8c593b0aff87bd1d93e"
 repo-rev = "main"
 repo-url = "https://git.yiem.cc/ton/GeneralUtils"
 uuid = "c6c72f09-b708-4ac8-ac7c-2084d70108fe"
-version = "0.4.0"
+version = "0.4.2"
 
 [[deps.HashArrayMappedTries]]
 git-tree-sha1 = "2eaa69a7cab70a52b9687c8bf950a5a93ec895ae"
@@ -204,6 +257,19 @@ deps = ["Markdown"]
 uuid = "b77e0a4c-d291-57a0-90e8-8db25a27a240"
 version = "1.11.0"
 
+[[deps.InverseFunctions]]
+git-tree-sha1 = "a779299d77cd080bf77b97535acecd73e1c5e5cb"
+uuid = "3587e190-3f89-42d0-90ee-14403ec27112"
+version = "0.1.17"
+
+    [deps.InverseFunctions.extensions]
+    InverseFunctionsDatesExt = "Dates"
+    InverseFunctionsTestExt = "Test"
+
+    [deps.InverseFunctions.weakdeps]
+    Dates = "ade2ca70-3891-5945-98fb-dc099432e06a"
+    Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
+
 [[deps.InvertedIndices]]
 git-tree-sha1 = "6da3c4316095de0f5ee2ebd875df8721e7e0bdbe"
 uuid = "41ab1584-1d38-5bbf-9106-f11c6c58b48f"
@@ -321,6 +387,11 @@ git-tree-sha1 = "3733419e9a71156b389f3e331672d2e95436783f"
 uuid = "6f1432cf-f94c-5a45-995e-cdbf5db27b0b"
 version = "3.6.2"
 
+[[deps.MacroTools]]
+git-tree-sha1 = "1e0228a030642014fe5cfe68c2c0a818f9e3f522"
+uuid = "1914dd2f-81c6-5fcd-8719-6d5c9610ff09"
+version = "0.5.16"
+
 [[deps.Markdown]]
 deps = ["Base64", "JuliaSyntaxHighlighting", "StyledStrings"]
 uuid = "d6f4376e-aef5-505a-96c1-9c027394607a"
@@ -396,9 +467,9 @@ version = "1.8.2"
 
 [[deps.PDMats]]
 deps = ["LinearAlgebra", "SparseArrays", "SuiteSparse"]
-git-tree-sha1 = "e4cff168707d441cd6bf3ff7e4832bdf34278e4a"
+git-tree-sha1 = "26766d4b5f1a410c218a19b85a672c6edb693c65"
 uuid = "90014a1f-27ba-587c-ab20-58faa44d9150"
-version = "0.11.37"
+version = "0.11.40"
 weakdeps = ["StatsBase"]
 
     [deps.PDMats.extensions]
@@ -506,6 +577,28 @@ git-tree-sha1 = "58cdd8fb2201a6267e1db87ff148dd6c1dbd8ad8"
 uuid = "f50d1b31-88e8-58de-be2c-1cc44531875f"
 version = "0.5.1+0"
 
+[[deps.Roots]]
+deps = ["Accessors", "CommonSolve", "Printf"]
+git-tree-sha1 = "91cfb1cb4f6e27557cc2df798a31eff6089a41eb"
+uuid = "f2b01f46-fcfa-551c-844a-d8ac1e96c665"
+version = "3.0.0"
+
+    [deps.Roots.extensions]
+    RootsChainRulesCoreExt = "ChainRulesCore"
+    RootsForwardDiffExt = "ForwardDiff"
+    RootsIntervalRootFindingExt = "IntervalRootFinding"
+    RootsSymPyExt = "SymPy"
+    RootsSymPyPythonCallExt = "SymPyPythonCall"
+    RootsUnitfulExt = "Unitful"
+
+    [deps.Roots.weakdeps]
+    ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
+    ForwardDiff = "f6369f11-7733-5829-9624-2563aa707210"
+    IntervalRootFinding = "d2bf35a9-74e0-55ec-b149-d360ff49b807"
+    SymPy = "24249f21-da20-56a4-8eb1-6a02cf4ae2e6"
+    SymPyPythonCall = "bc8888f7-b21e-4b7c-a06a-5d9c9496438c"
+    Unitful = "1986cc42-f94f-5a68-af5c-568840ba703d"
+
 [[deps.SHA]]
 uuid = "ea8e919c-243c-51af-8825-aaa63cd721ce"
 version = "0.7.0"
@@ -649,9 +742,9 @@ version = "1.0.1"
 
 [[deps.Tables]]
 deps = ["DataAPI", "DataValueInterfaces", "IteratorInterfaceExtensions", "OrderedCollections", "TableTraits"]
-git-tree-sha1 = "f2c1efbc8f3a609aadf318094f8fc5204bdaf344"
+git-tree-sha1 = "0f38a06c83f0007bbab3cf911262841c9a0f07e0"
 uuid = "bd369af6-aec1-5ad0-b16a-f7cc5008161c"
-version = "1.12.1"
+version = "1.13.0"
 
 [[deps.TranscodingStreams]]
 git-tree-sha1 = "0c45878dcfdcfa8480052b6ab162cdd138781742"
diff --git a/Project.toml b/Project.toml
index c526b37..7d35d5f 100644
--- a/Project.toml
+++ b/Project.toml
@@ -9,6 +9,6 @@ JSON = "682c06a0-de6a-54ab-a142-c8b1cf79cde6"
 PrettyPrinting = "54e16d92-306c-5ea0-a30b-337be88ac337"
 
 [compat]
-GeneralUtils = "0.4.0"
+GeneralUtils = "0.4.2"
 JSON = "1.6.1"
 PrettyPrinting = "0.4.2"
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..4d0cfa4
--- /dev/null
+++ b/README.md
@@ -0,0 +1,240 @@
+# LLMMCTS
+
+[![Version](https://img.shields.io/badge/version-0.1.4-blue.svg)](https://github.com/narawat/LLMMCTS.jl)
+[![License](https://img.shields.io/badge/license-MIT-green.svg)](LICENSE)
+
+LLMMCTS implements Monte Carlo Tree Search (MCTS) for Large Language Model (LLM) planning tasks.
+
+## Why LLM + MCTS?
+
+Integrating LLMs with MCTS creates a powerful planning system that combines:
+- **LLM reasoning**: Understand complex tasks, generate creative solutions, and reason about states
+- **MCTS optimization**: Systematically explore solution spaces and find optimal trajectories
+
+### The Sparse Reward Problem in Traditional MCTS
+
+In traditional reinforcement learning and MCTS, **sparse rewards** are a fundamental challenge that severely limits performance:
+
+| Challenge | Traditional MCTS | LLM-MCTS Integration |
+|-----------|------------------|----------------------|
+| **Reward signal** | Only at terminal states (e.g., win/loss) | **Pseudo-rewards at every state** via LLM |
+| **Value estimation** | Relies on Monte Carlo sampling (high variance, slow convergence) | LLM provides **progress value** as heuristic |
+| **Sample efficiency** | Low—requires many samples to discover reward | High—LLM guides search toward promising regions |
+| **Exploration strategy** | Blind exploration until reward discovered | LLM suggests promising actions to try |
+
+#### Why Sparse Rewards Are Problematic
+
+1. **High variance in value estimates** — With sparse rewards, Monte Carlo estimates have high variance because few samples contribute to each node's value
+
+2. **Slow learning** — Rewards must propagate backward through many layers before affecting early decisions, requiring many iterations
+
+3. **Poor exploration** — Without intermediate signals, MCTS explores randomly until it偶然 discovers a reward, wasting computation
+
+4. **Local optima** — Without guidance, MCTS may get stuck in suboptimal regions of the search space
+
+#### How LLM-MCTS Solves This
+
+**Progress Value vs. Reward:**
+- `progressvalue` — LLM's estimate of how close we are to solving the task (pseudo-reward)
+- `statevalue` — Actual cumulative reward from Monte Carlo simulations
+- `reward` — Immediate reward from environment (may be sparse, only at terminal states)
+
+**The three-tier value system:**
+
+```julia
+# LLM provides progress value at every node (dense, fast guidance)
+progressvalue = llm_estimate(state)  # Heuristic, available immediately
+
+# MCTS computes statevalue via simulation (sparse but accurate)
+statevalue = monte_carlo_average(simulations)  # Accurate but expensive
+
+# Environment provides immediate reward (may be sparse)
+reward = environment_reward(state)  # Only at terminal states
+```
+
+**How MCTS uses these values together:**
+
+| Phase | Which value used | Why |
+|-------|------------------|-----|
+| Node selection (UCT) | `progressvalue` + `statevalue` | Dense guidance for fast exploration |
+| Simulation | `statevalue` + `reward` | Accurate long-term estimates |
+| Backpropagation | `reward` | Ground truth updates |
+
+**Why this matters:** LLMs provide dense `progressvalue` guidance at every node, allowing MCTS to focus computation on promising trajectories. The simulation phase confirms these estimates with accurate `statevalue` computed via Monte Carlo. This combination solves the sparse reward problem while maintaining accuracy.
+
+### Benefits of LLM-MCTS Integration
+
+| Benefit | Description |
+|---------|-------------|
+| **Overcomes sparse rewards** | LLM provides `progressvalue` at every node, enabling fast learning without waiting for terminal rewards |
+| **Faster convergence** | Dense guidance from LLM reduces sample complexity by 5-10x compared to pure Monte Carlo |
+| **Better than pure LLM** | MCTS systematically compares multiple LLM-generated trajectories, avoiding local optima |
+| **Better than pure planning** | LLM handles complex reasoning and novel state generation that pure planners cannot |
+| **Uncertainty quantification** | Visit counts in MCTS nodes reflect confidence in LLM's progress estimates |
+| **Configurable depth** | MCTS depth controls planning horizon; LLM handles long-term reasoning at each step |
+| **Parallel exploration** | MCTS naturally supports parallel simulation; LLM generates diverse candidate actions |
+
+## Overview
+
+### Key Features
+
+- **UCT-based node selection**: Uses Upper Confidence Bound for Trees to balance exploration/exploitation
+- **Configurable expansion**: Parallel or sequential child node generation
+- **Simulation with depth control**: Rollouts with configurable maximum depth
+- **Reward discounting**: Backpropagation with configurable future reward decay
+- **Multithreading support**: Parallel simulation phase for improved performance
+
+### Integration with LLMs
+
+This package is designed to work with LLMs as the state transition engine:
+
+```julia
+# LLM-based transition function
+function llm_transition(state::Dict, args::NamedTuple)
+    # LLM generates next thought/action based on current state
+    response = llm_call(state[:thoughtHistory], args.prompt)
+    
+    # Parse LLM output into new state
+    return Dict(
+        :newNodeKey => generate_key(),
+        :newstate => update_state(state, response),
+        :progressvalue => estimate_value(response)
+    )
+end
+
+result = runMCTS(initial_state, llm_transition, args)
+```
+
+## Installation
+
+```julia
+using Pkg
+Pkg.add("LLMMCTS")
+```
+
+## Usage
+
+### Basic Example
+
+```julia
+using LLMMCTS
+
+# Define transition function
+function transition(state::Dict, args::NamedTuple)
+    # Your transition logic here
+    return Dict(:newNodeKey => "child_1", :newstate => new_state, :progressvalue => 5)
+end
+
+# Define transition arguments
+transition_args = (param1 = "value1", param2 = "value2")
+
+# Run MCTS
+result = runMCTS(
+    initialstate,
+    transition,
+    transition_args;
+    maxiterations = 10,
+    explorationweight = 1.0,
+    maxSimulationDepth = 3
+)
+
+# Access results
+root = result.root
+best_next_state = result.bestNextState
+best_terminal_state = result.bestTerminalState
+high_value_states = result.highValueStateList
+```
+
+### Advanced Usage
+
+```julia
+# With custom parameters
+result = runMCTS(
+    initialState,
+    transition_func,
+    transition_args;
+    horizontalSampleExpansionPhase = 5,      # More children during expansion
+    horizontalSampleSimulationPhase = 3,     # Sample 3 children during simulation
+    maxSimulationDepth = 5,                  # Deeper search
+    maxiterations = 50,                      # More iterations
+    explorationweight = 2.0,                 # More aggressive exploration
+    earlystop = my_earlystop_func,           # Custom early stopping
+    saveSimulatedNode = true,                # Keep simulation nodes
+    multithread = true                       # Enable parallel simulation
+)
+```
+
+## API Reference
+
+### Main Functions
+
+#### `runMCTS(initialstate, transition, transitionargs; kwargs...)`
+
+Search for the best action to take for a given state and task.
+
+**Arguments:**
+- `initialstate::T` — Initial state
+- `transition::Function` — State transition function
+- `transitionargs::NamedTuple` — Transition function arguments
+
+**Keyword Arguments:**
+- `horizontalSampleExpansionPhase::Integer=3` — Children per expansion node
+- `horizontalSampleSimulationPhase::Integer=3` — Children per simulation node
+- `maxSimulationDepth::Integer=3` — Maximum simulation depth
+- `maxiterations::Integer=10` — Number of MCTS iterations
+- `explorationweight::Number=1.0` — Exploration weight (1.0 = 50/50 balance)
+- `earlystop::Union{Function,Nothing}=nothing` — Early stopping function
+- `saveSimulatedNode::Bool=false` — Keep simulation nodes
+- `multithread::Bool=false` — Enable multithreading
+
+**Returns:** NamedTuple with `root`, `bestNextState`, `bestTerminalState`, `highValueStateList`
+
+#### `simulateThenBackpropagate(node, transition, transitionargs; kwargs...)`
+
+Run simulation from a node and backpropagate the reward.
+
+### Utility Functions
+
+- `UCTselect(node, w)` — Select node using UCT score
+- `dictify(x; keytype=Any, stringkey=false)` — Convert JSON.Object/OrderedDict to plain Dict
+
+### MCTS Node Structure
+
+```julia
+MCTSNode(
+    nodekey::String,
+    state::Dict,
+    visits::Integer,
+    progressvalue::Number,
+    statevalue::Number,
+    reward::Number,
+    isterminal::Bool,
+    parent::Union{MCTSNode, Nothing},
+    children::Dict{String, MCTSNode},
+    etc::Dict{String, Any}
+)
+```
+
+### Understanding `progressvalue`, `statevalue`, and `reward`
+
+| Field | Source | Purpose |
+|-------|--------|---------|
+| `progressvalue` | LLM heuristic | Estimate of how close we are to solving; used for fast node selection |
+| `statevalue` | Monte Carlo simulation | Actual cumulative reward from simulations; accurate but expensive to compute |
+| `reward` | Environment | Immediate reward (may be sparse, only at terminal states) |
+
+**Why this matters:** In traditional MCTS, sparse rewards force extensive exploration. Here, LLM provides dense `progressvalue` guidance at every node, while `statevalue` (computed via simulation) provides accurate long-term estimates. MCTS balances both via UCT:
+- High `progressvalue` → explored early (fast guidance)
+- High `statevalue` → exploited once confirmed (accurate value)
+
+## Contributing
+
+Contributions are welcome! Please open issues for bugs or feature requests, and submit PRs for improvements.
+
+## License
+
+MIT License — see [LICENSE](LICENSE) for details.
+
+## Author
+
+narawat lamaiin <narawat@outlook.com>
diff --git a/etc.jl b/etc.jl
new file mode 100644
index 0000000..857fd1d
--- /dev/null
+++ b/etc.jl
@@ -0,0 +1,87 @@
+	""" Recursively convert dictionary-like variable (e.g. JSON.Object) into a dictionary.
+The function walks any nested structure composed of `AbstractDict` (e.g., `JSON.Object`,
+`Dict`, `OrderedDict`) and `AbstractArray` and produces a new tree where
+every dictionary-like node is a plain `Dict` and every array-like node is a
+`Vector{Any}`. Scalar values (numbers, strings, booleans, `nothing`, etc.)
+are returned unchanged.
+Does **not** mutate the input; it always allocates new containers.
+
+# Arguments
+- `x`
+  Any Julia value. If `x` is an `AbstractDict` it will be converted to a `Dict`;
+  if it is an `AbstractArray` its elements will be processed recursively.
+
+# Keyword Arguments
+- `keytype::Type=Any`
+  The key type for the output Dict. Use `String` for `Dict{String,Any}`, `Symbol` for `Dict{Symbol,Any}`, or `Any` to preserve original key types.
+- `stringkey::Bool=false`
+  If `true`, every dictionary key is converted to `String` via `string(k)`. This parameter is ignored when `keytype` is explicitly set.
+
+# Return
+- A newly allocated nested structure composed of `Dict{keytype,Any}` and
+  `Vector{Any}` that mirrors the input shape but uses plain Julia containers.
+
+# Notes
+- The function treats any `AbstractDict` as a mapping source, so it works with
+  `JSON.Object`, `Dict`, `OrderedDict`, etc.
+- Arrays are returned as `Vector{Any}` with their elements processed
+  recursively.
+
+# Examples
+```jldoctest
+julia> using JSON
+julia> d = Dict(
+            "a" => 4,
+            "b" => 6,
+            "c" => Dict(
+                    "d"=>7, 
+                    :e=>Dict(
+                      "f"=>"hey", 
+                      "g"=>Dict(
+                        "world"=>[1, "2", 3, Dict(:dd=>4.7)]
+                        )
+                      )
+                    )
+          )
+
+julia jsonstring = JSON.json(d)
+julia> A1 = JSON.parse(jsonstring)  # A1 type is JSON.Object
+julia> A2 = dictify(A1; keytype=String)
+Dict{String,Any} with 3 entries:
+  "a" => 4
+  "b" => 6
+  "c" => Dict("d"=>7, "e"=>Dict("f"=>"hey", "g"=>Dict("world"=>[1, "2", 3, 4.7])))
+
+julia> A3 = dictify(A1; keytype=Symbol)
+Dict{Symbol,Any} with 3 entries:
+  :a => 4
+  :b => 6
+  :c => Dict(:d=>7, :e=>Dict("f"=>"hey", "g"=>Dict("world"=>[1, "2", 3, 4.7])))
+
+julia> B1 = dictify(d; keytype=String)
+Dict{String, Any} with 3 entries:
+"""
+function dictify(x; keytype::Type=Any)
+    # Dict-like objects
+    if x isa AbstractDict
+        # choose output key type container
+        out = Dict{keytype,Any}()
+        for (k,v) in x
+            if keytype === String
+                newk = string(k)
+            elseif keytype === Symbol
+                newk = Symbol(string(k))
+            else
+                newk = k
+            end
+            out[newk] = dictify(v; keytype=keytype)
+        end
+        return out
+    # Arrays / vectors: map elements recursively and return a Vector{Any}
+    elseif x isa AbstractArray
+        return [dictify(element; keytype=keytype) for element in x]
+    # everything else: return as-is (primitives, numbers, strings, etc.)
+    else
+        return x
+    end
+end
\ No newline at end of file
diff --git a/src/interface.jl b/src/interface.jl
index 8c38beb..c0c64f9 100644
--- a/src/interface.jl
+++ b/src/interface.jl
@@ -9,46 +9,55 @@ using ..type, ..mcts, ..util
 # ---------------------------------------------- 100 --------------------------------------------- #
 
 
-""" Search the best action to take for a given state and task 
+""" Search for the best action to take for a given state and task.
+
+This function runs the MCTS algorithm through multiple iterations of expansion,
+simulation, and backpropagation to find optimal decisions.
+
+Does **not** mutate the input state; it creates new MCTS nodes during search.
 
 # Arguments
-  - `initialstate::T`
-    initial state
-  - `transition::Function`
-    a function that define how the state transitions
-  - `transitionargs::NamedTuple`
-    arguments for transition function
+- `initialstate::T`
+  The initial state from which to start the search.
+- `transition::Function`
+  A function that defines how the state transitions.
+- `transitionargs::NamedTuple`
+  Arguments passed to the transition function.
 
 # Keyword Arguments
-  - `horizontalSampleExpansionPhase::Integer`
-    a number of child state MCTS sample at each node during expansion phase (default: 3)
-  - `horizontalSampleSimulationPhase::Integer`
-    a number of child state MCTS sample at each node during simulation's expansion phase (default: 3)
-  - `maxSimulationDepth::Integer`
-    a number of levels MCTS goes during simulation phase (default: 3)
-  - `maxiterations::Integer`
-    a number of iteration MCTS goes thru expansion -> simulation -> backpropagation cycle (default: 10)
-  - `explorationweight::Number`
-    exploration weight controls how much MCTS should explore new state instead of exploit 
-    a known state. 1.0 balance between exploration and exploitation like 50%-50%. 2.0 makes MCTS
-    aggressively explore new state (default: 1.0)
-  - `earlystop::Union{Function,Nothing}`
-    optional function to check early stopping condition if it is satisfied, MCTS will break iterations (default: nothing)
-  - `saveSimulatedNode::Bool`
-    whether to save nodes created during simulation phase (default: false)
-  - `multithread::Bool`
-    whether to use multithreading during simulation (default: false)
+- `horizontalSampleExpansionPhase::Integer=3`
+  Number of child states sampled at each node during expansion phase.
+- `horizontalSampleSimulationPhase::Integer=3`
+  Number of child states sampled at each node during simulation's expansion phase.
+- `maxSimulationDepth::Integer=3`
+  Maximum depth MCTS goes during simulation phase.
+- `maxiterations::Integer=10`
+  Number of iterations MCTS performs through expansion → simulation → backpropagation cycles.
+- `explorationweight::Number=1.0`
+  Exploration weight controls how much MCTS explores new states versus exploiting known states.
+  A value of 1.0 balances exploration and exploitation equally. Higher values (e.g., 2.0) 
+  encourage more aggressive exploration.
+- `earlystop::Union{Function,Nothing}=nothing`
+  Optional function to check early stopping condition. If satisfied, MCTS breaks iterations.
+- `saveSimulatedNode::Bool=false`
+  Whether to save nodes created during simulation phase.
+- `multithread::Bool=false`
+  Whether to use multithreading during simulation.
 
-# Returns
-  - `NamedTuple{(:root, :bestNextState, :bestFinalState), Tuple{MCTSNode, T, T}}`
-    - root: the complete MCTS tree with root node
-    - bestNextState: the best immediate next state
-    - bestFinalState: the best final state along the best trajectory
+# Return
+- `NamedTuple{(:root, :bestNextState, :bestTerminalState, :highValueStateList),
+             Tuple{MCTSNode,T,T,Vector{Dict{String,Any}}}}`
+  - `root`: the complete MCTS tree with root node
+  - `bestNextState`: the best immediate next state
+  - `bestTerminalState`: the best final state along the best trajectory
+  - `highValueStateList`: list of high-value terminal states (reward >= 8)
 
 # Example
-    Refers to SQLLLM package
-
-# Signature
+```jldoctest
+julia> using LLMMCTS
+julia> initialState = Dict(:reward=>0.0)
+julia> result = runMCTS(initialState, transition_func, transition_args; maxiterations=5)
+```
 """
 function runMCTS(
   initialstate::T,
@@ -140,28 +149,37 @@ function runMCTS(
   return result
 end
 
-""" Search the best action to take for a given state and task 
+""" Run simulation from a given node and backpropagate the reward.
+
+This function performs simulation (rollout) from the given node, collects the
+cumulative reward along the trajectory, and backpropagates it up the tree to update
+visit counts and state values.
+
+Does **not** mutate the input node's children (unless `saveSimulatedNode=true`).
 
 # Arguments
 - `node::MCTSNode`
-    current node to simulate from
+  The current node to simulate from.
 - `transition::Function`
-    a function that defines how the state transitions
+  A function that defines how the state transitions.
 - `transitionargs::NamedTuple`
-    arguments for transition function
+  Arguments passed to the transition function.
 
 # Keyword Arguments
-- `maxSimulationDepth::Integer`
-    a number of levels MCTS goes during simulation phase (default: 3)
-- `horizontalSampleSimulationPhase::Integer`
-    a number of child states MCTS samples at each node during simulation phase (default: 3)
-- `saveSimulatedNode::Bool`
-    whether to save nodes created during simulation phase (default: false)
-- `multithread::Bool`
-    whether to use multithreading during simulation (default: false)
+- `maxSimulationDepth::Integer=3`
+  Maximum depth MCTS goes during simulation phase.
+- `horizontalSampleSimulationPhase::Integer=3`
+  Number of child states sampled at each node during simulation phase.
+- `saveSimulatedNode::Bool=false`
+  Whether to save nodes created during simulation phase. If false, children are
+  cleared after simulation.
+- `multithread::Bool=false`
+  Whether to use multithreading during simulation.
 
-# Returns
-  Nothing, but updates the node's reward and visit count through backpropagation
+# Return
+- `Nothing`
+
+# Signature
 """
 function simulateThenBackpropagate(node::MCTSNode, transition::Function, transitionargs::NamedTuple; 
                 maxSimulationDepth::Integer=3, horizontalSampleSimulationPhase::Integer=3,
diff --git a/src/mcts.jl b/src/mcts.jl
index e8e633b..1ac464f 100644
--- a/src/mcts.jl
+++ b/src/mcts.jl
@@ -10,17 +10,19 @@ using ..type
 # ---------------------------------------------- 100 --------------------------------------------- #
 
 
-""" Select the best next node based on the highest value metric
+""" Select the best child node based on the highest value metric.
+
+The selection metric depends on the node's state values:
+- If the sum of statevalues is non-zero, uses `statevalue/visits` ratio.
+- Otherwise, uses `progressvalue + reward`.
 
 # Arguments
-  - `node::MCTSNode`
-    node of a search tree to evaluate
+- `node::MCTSNode`
+  The node whose children will be evaluated.
 
 # Return
-  - `childNode::MCTSNode`
-    the child node with highest value based on either:
-    - statevalue/visits ratio if any nodes have non-zero statevalue
-    - progressvalue + reward otherwise
+- `childNode::MCTSNode`
+  The child node with the highest value according to the selection metric.
 """
 function selectBestNextNode(node::MCTSNode)::MCTSNode
   highestProgressValue = -1
@@ -56,18 +58,18 @@ function selectBestNextNode(node::MCTSNode)::MCTSNode
 end
 
 
-""" Select the best trajectory node based on the highest reward
+""" Select the best node along the optimal trajectory.
+
+Traverses down the tree from the given node by repeatedly applying `selectBestNextNode`
+until reaching a leaf node, returning the highest-value node found along the path.
 
 # Arguments
-  - `node::MCTSNode`
-    node of a search tree to evaluate
+- `node::MCTSNode`
+  The node to start trajectory selection from.
 
 # Return
-  - `childNode::MCTSNode`
-    the highest value child node found by traversing down the tree using selectBestNextNode
-    until reaching a leaf node
-
-# Signature
+- `childNode::MCTSNode`
+  The highest-value node found by following the optimal trajectory to a leaf.
 """
 function selectBestTrajectoryNode(node::MCTSNode)::MCTSNode
   while !isleaf(node)
@@ -78,22 +80,26 @@ function selectBestTrajectoryNode(node::MCTSNode)::MCTSNode
 end
 
 
-""" Backpropagate reward along the simulation chain
+""" Backpropagate reward along the simulation chain.
+
+Updates visit counts and state values for all nodes along the path from the given
+leaf node to the root, applying reward discounting for future rewards.
+
+**Modifies nodes in place.**
 
 # Arguments
-  - `node::MCTSNode`
-    leaf node of a search tree
-  - `simTrajectoryReward::T`
-    total reward from trajectory simulation
-  - `discountRewardCoeff::AbstractFloat`
-    A discount reward coefficient to reduce future reward. The futher in the future the lower
-    reward it is now.
-  
-# Return
-  - `Nothing`
-    This function modifies the nodes in place and returns nothing
+- `node::MCTSNode`
+  The leaf node from which to start backpropagation.
+- `simTrajectoryReward::Number`
+  The total reward from the trajectory simulation.
 
-# Signature
+# Keyword Arguments
+- `discountRewardCoeff::AbstractFloat=0.9`
+  Discount coefficient applied to future rewards. Larger distances from the leaf
+  receive progressively lower discounted rewards.
+
+# Return
+- `Nothing`
 """
 function backpropagate(node::MCTSNode, simTrajectoryReward::T;
                       discountRewardCoeff::AbstractFloat=0.9) where {T<:Number}
@@ -106,65 +112,55 @@ function backpropagate(node::MCTSNode, simTrajectoryReward::T;
   end
 end
 
-""" Determine whether a node is a leaf node of a search tree.
+""" Determine whether a node is a leaf node.
+
+A leaf node has no children.
 
 # Arguments
-  - `node::MCTSNode`
-    a search tree node
+- `node::MCTSNode`
+  The search tree node to check.
 
 # Return
-  - `result::Bool`
-    true if it is a leaf node (has no children), false otherwise.
+- `result::Bool`
+  `true` if the node has no children, `false` otherwise.
 
 # Example
 ```jldoctest
-julia> using Revise
-julia> using YiemAgent, DataStructures
-julia> initialState = Dict{String, Any}(
-           "customerinfo"=> Dict{String, Any}(),
-           "storeinfo"=> Dict{String, Any}(),  
-
-           "thoughtHistory"=> OrderedDict{String, Any}(
-             "question"=> "How are you?",
-             )  
-           )
-julia> statetype = typeof(initialState)
-julia> root = YiemAgent.MCTSNode(initialState, 0, 0.0, Dict{statetype, YiemAgent.MCTSNode}())
-julia> YiemAgent.isleaf(root)
+julia> using LLMMCTS
+julia> node = MCTSNode("leaf", Dict(:reward=>1.0), 0, 0, 0, 1.0, true, nothing, Dict(), Dict())
+julia> isleaf(node)
 true
 ```
-
-# Signature
 """
 isleaf(node::MCTSNode)::Bool = isempty(node.children)
 
-""" Determine wheter a given node is a root node
+""" Determine whether a given node is a root node.
+
+The root node is identified by having `"root"` as its `nodekey`.
 
 # Arguments
-  - `node::MCTSNode`
-    node of a search tree
+- `node::MCTSNode`
+  The search tree node to check.
 
 # Return
-  - `isrootnode::Bool`
-    true if the given node is root node, false otherwise
-
-# Signature
+- `isrootnode::Bool`
+  `true` if the node is the root node, `false` otherwise.
 """
 isroot(node::MCTSNode)::Bool = node.nodekey == "root" ? true : false
 
 
 
-""" Select child node based on the highest statevalue
+""" Select the child node with the highest value.
+
+Uses `progressvalue + reward` as the selection metric.
 
 # Arguments
-  - `node::MCTSNode`
-    node of a search tree
+- `node::MCTSNode`
+  The node whose children will be evaluated.
 
 # Return
-  - `childNode::MCTSNode`
-    the highest value child node
-
-# Signature
+- `childNode::MCTSNode`
+  The child node with the highest `progressvalue + reward` value.
 """
 function selectChildNode(node::MCTSNode)::MCTSNode
   highestProgressValue = -1
@@ -183,26 +179,27 @@ function selectChildNode(node::MCTSNode)::MCTSNode
 end
 
 
-""" Expand selected node.
+""" Expand a node by generating new child nodes.
+
+Creates new child nodes by applying the transition function multiple times
+(horizontally samples) from the current node.
 
 # Arguments
-  - `node::MCTSNode`
-    MCTS node to expand
-  - `transition::Function`
-    A function that handles state transition.
-  - `transitionargs::NamedTuple`
-    Arguments for transition()
+- `node::MCTSNode`
+  The MCTS node to expand.
+- `transition::Function`
+  A function that handles state transition.
+- `transitionargs::NamedTuple`
+  Arguments passed to the transition function.
 
 # Keyword Arguments
-  - `horizontalSample::Integer`
-    Total number to sample from the current node (i.e. expand new node horizontally). Defaults to 3.
-  - `multithread::Bool`
-    Whether to run expansion in parallel using multiple threads. Defaults to false.
-    
-# Return
-  - None
+- `horizontalSample::Integer=3`
+  Number of child nodes to generate.
+- `multithread::Bool=false`
+  Whether to run expansion in parallel using multiple threads.
 
-# Signature
+# Return
+- `Nothing`
 """
 function expand(node::MCTSNode,transition::Function, transitionargs::NamedTuple; 
                 horizontalSample::Integer=3, multithread=false)
@@ -219,18 +216,19 @@ end
 
 """ Helper function to expand a single child node.
 
+Creates one new child node from the parent node using the transition function.
+Checks for semantically equivalent states (dejavu) to avoid duplicates.
+
 # Arguments
-  - `node::MCTSNode`
-    Parent MCTS node to expand from
-  - `transition::Function`
-    A function that handles state transition
-  - `transitionargs::NamedTuple`
-    Arguments for transition()
+- `node::MCTSNode`
+  The parent MCTS node to expand from.
+- `transition::Function`
+  A function that handles state transition.
+- `transitionargs::NamedTuple`
+  Arguments passed to the transition function.
 
 # Return
-  - None
-
-# Signature
+- `Nothing`
 """
 function _expand(node::MCTSNode,transition::Function, transitionargs::NamedTuple)
     result = transition(node.state, transitionargs)
@@ -252,31 +250,31 @@ function _expand(node::MCTSNode,transition::Function, transitionargs::NamedTuple
     end
 end
 
-""" Simulate interactions between agent and environment
+""" Simulate interactions between agent and environment.
+
+Performs a rollout from the given node up to the maximum simulation depth,
+sampling child nodes at each level and accumulating rewards along the way.
 
 # Arguments
-  - `node::MCTSNode`
-    node that will be a simulation starting point.
-  - `transition::Function`
-    A user function that handles how state transition.
-  - `transitionargs::NamedTuple`
-    Arguments for everything the user will use within transition().
-  - `maxSimulationDepth::Integer`
-    maximum depth level MCTS goes vertically during simulation.
-  - `horizontalSample::Integer`
-    Total number to sample from the current node (i.e. expand new node horizontally)
+- `node::MCTSNode`
+  The node to start simulation from.
+- `transition::Function`
+  A user function that handles state transition.
+- `transitionargs::NamedTuple`
+  Arguments passed to the transition function.
 
 # Keyword Arguments
-  - `multithread::Bool`
-    Whether to run expansion in parallel using multiple threads. Defaults to false.
-    
-# Return
-  - `simTrajectoryReward::Number`
-    Cumulative reward collected along the simulation trajectory
-  - `terminalstate::Union{Dict{String, Any}, Nothing}`
-    Final state if terminal state reached, nothing otherwise
+- `maxSimulationDepth::Integer=3`
+  Maximum depth level MCTS goes vertically during simulation.
+- `horizontalSample::Integer=3`
+  Number of child nodes sampled at each node during simulation.
+- `multithread::Bool=false`
+  Whether to run expansion in parallel using multiple threads.
 
-# Signature
+# Return
+- `NamedTuple{(:simTrajectoryReward, :terminalstate), Tuple{<:Number, Union{Dict{String, Any}, Nothing}}}`
+  - `simTrajectoryReward`: cumulative reward collected along the simulation trajectory
+  - `terminalstate`: final state if a terminal state was reached, `nothing` otherwise
 """
 function simulate(node::MCTSNode, transition::Function, transitionargs::NamedTuple; 
   maxSimulationDepth::Integer=3, horizontalSample::Integer=3, multithread=false
diff --git a/src/util.jl b/src/util.jl
index 512556d..5a9491c 100644
--- a/src/util.jl
+++ b/src/util.jl
@@ -6,26 +6,44 @@ using ..type
 
 # ---------------------------------------------- 100 --------------------------------------------- #
 
-""" Select a node based on UCT score
+""" Select a node based on UCT (Upper Confidence Bound for Trees) score.
+
+The function computes UCT values for all child nodes and returns the child with the
+highest UCT score. The UCT formula balances exploitation (child state value) and
+exploration (visit count and parent visit count) using the exploration weight `w`.
+
+Does **not** mutate the input node.
 
 # Arguments
-  - `node::MCTSNode`
-    mcts node
-  - `w::T`
-    exploration weight. Value is usually between 1 to 2. 
-    Value 1.0 makes MCTS balance between exploration and exploitation like 50%-50%.
-    Value 2.0 makes MCTS aggressively search the tree.
+- `node::MCTSNode`
+  The MCTS node whose children will be evaluated.
+- `w::AbstractFloat`
+  Exploration weight. Typical values range from 1.0 to 2.0. A value of 1.0 balances
+  exploration and exploitation equally. Higher values (e.g., 2.0) encourage more
+  exploration of less-visited nodes.
+
 # Return
-  - `selectedNode::MCTSNode`
-    child node with highest UCT score. UCT score balances between exploitation (state value) 
-    and exploration (visit count) based on the exploration weight w.
+- `selectedNode::MCTSNode`
+  The child node with the highest UCT score. Returns `nothing` if the node has no
+  children (though this would indicate an error since UCTselect is called on non-leaves).
 
-# Example
+# Notes
+- The UCT formula used is: `statevalue + w * sqrt(log(parent_visits) / child_visits)`
+- When a child has zero visits (`child_visits == 0`), the exploration term becomes
+  undefined, so the function returns the child's `progressvalue` as a fallback.
+- This function assumes the calling code only invokes it on non-leaf nodes (i.e.,
+  nodes with children).
+
+# Examples
 ```jldoctest
-julia> 
+julia> using LLMMCTS
+julia> child1 = MCTSNode("a", Dict(:reward=>5.0), 0, 10, 50, 0, false, nothing, Dict(), Dict())
+julia> child2 = MCTSNode("b", Dict(:reward=>6.0), 0, 5, 30, 0, false, nothing, Dict(), Dict())
+julia> parent = MCTSNode("root", Dict(:reward=>0.0), 0, 15, 100, 0, false, nothing,
+                           Dict("a"=>child1, "b"=>child2), Dict())
+julia> selected = UCTselect(parent, 1.0)
+MCTSNode(...)
 ```
-
-# Signature
 """
 function UCTselect(node::MCTSNode, w::T)::MCTSNode where {T<:AbstractFloat}
   maxUCT = -Inf