# Tool Use Example - MCTS with External Tools

This example shows how MCTS can coordinate with external tools (like APIs, databases, or other services).

```julia
using LLMMCTS

# Simulated tool interface
struct Tool
    name::String
    description::String
end

const AVAILABLE_TOOLS = [
    Tool("calculator", "Perform mathematical calculations"),
    Tool("web_search", "Search the web for information"),
    Tool("database_query", "Query a database")
]

# State tracks which tools have been used and their results
function tool_use_transition(state::Dict, args::NamedTuple)
    current_step = get(state, :step, 0)
    tools_used = get(state, :tools_used, String[])
    
    # LLM would decide which tool to use
    # For this example, we try tools in order
    tool_idx = (current_step - 1) % length(AVAILABLE_TOOLS) + 1
    
    if tool_idx > length(AVAILABLE_TOOLS)
        # All tools tried, return terminal state
        newstate = Dict(
            :step => current_step + 1,
            :tools_used => tools_used,
            :reward => 8.0,
            :isterminal => true
        )
        return Dict(
            :newNodeKey => "all_tools_tried",
            :newstate => newstate,
            :progressvalue => 8.0
        )
    end
    
    tool = AVAILABLE_TOOLS[tool_idx]
    
    # Simulate tool execution
    tool_result = "Tool '$(tool.name)' executed successfully"
    
    # Calculate reward based on progress
    progress = length(tools_used) / length(AVAILABLE_TOOLS)
    reward = progress * 5
    
    # Progress value: LLM estimates how close we are to solving
    progressvalue = progress * 10
    
    new_tools_used = vcat(tools_used, tool.name)
    
    newstate = Dict(
        :step => current_step + 1,
        :tools_used => new_tools_used,
        :current_tool => tool.name,
        :tool_result => tool_result,
        :reward => reward,
        :isterminal => false
    )
    
    return Dict(
        :newNodeKey => "tool_$(tool.name)_$current_step",
        :newstate => newstate,
        :progressvalue => progressvalue
    )
end

# Initial state
initialstate = Dict(
    :step => 0,
    :tools_used => String[],
    :reward => 0,
    :isterminal => false
)

# Transition arguments
transitionargs = (max_tools = 3,)

# Run MCTS
result = runMCTS(
    initialstate,
    tool_use_transition,
    transitionargs;
    maxiterations = 20,
    explorationweight = 1.2,
    maxSimulationDepth = 4,
    horizontalSampleExpansionPhase = 3
)

# Display results
println("Available tools:")
for tool in AVAILABLE_TOOLS
    println("  - $(tool.name): $(tool.description)")
end
println()
println("Best tool usage sequence:")
for tool in result.bestTerminalState[:tools_used]
    println("  → Used: $tool")
end
println()
println("Root node visits: ", result.root.visits)
println("High value states found: ", length(result.highValueStateList))
```