diff --git a/src/agentCore.jl b/src/agentCore.jl
index 4de1215..7031295 100644
--- a/src/agentCore.jl
+++ b/src/agentCore.jl
@@ -202,7 +202,6 @@ function _process_message(agent::yiemAgent)::assistantMessage
       push!(agent._state.messages, user_msg)
     end
 
-
     # call agent.prepareContext()
     preparedContext = agent.prepareContext(agent._state)
 
@@ -998,7 +997,7 @@ function executeToolCalls(
     hasSequential = false
     for tc in toolCalls
         for t in context.tools
-            if t.name == tc.name && get(t.executionMode, "parallel") == "sequential"
+            if t.name == tc.name && !t.parallelToolExecute
                 hasSequential = true
                 break
             end
diff --git a/src/type.jl b/src/type.jl
index f573e67..0da023f 100644
--- a/src/type.jl
+++ b/src/type.jl
@@ -13,6 +13,21 @@ struct Usage
     outputTokens::Int64
 end
 
+# ------------------------------------------------------------------------------------------------ #
+#                                       Message content types                                      #
+# ------------------------------------------------------------------------------------------------ #
+
+abstract type messageContent end              # Base type for message content
+
+struct textContent <: messageContent          # Plain text message content
+    text::String                              # The text content
+end
+
+struct imageContent <: messageContent         # Image message content
+    data::String                              # Base64-encoded image data
+    mimeType::String                          # MIME type (e.g., "image/png")
+end
+
 
 # ------------------------------------------------------------------------------------------------ #
 #                                           Message types                                          #
@@ -128,22 +143,6 @@ function toolResultMessage(; role="tool", toolCallId="", toolName="",
     return toolResultMessage(role, toolCallId, toolName, content, details, usage, addedToolNames, isError, timestamp)
 end
 
-
-# ------------------------------------------------------------------------------------------------ #
-#                                       Message content types                                      #
-# ------------------------------------------------------------------------------------------------ #
-
-abstract type messageContent end              # Base type for message content
-
-struct textContent <: messageContent          # Plain text message content
-    text::String                              # The text content
-end
-
-struct imageContent <: messageContent         # Image message content
-    data::String                              # Base64-encoded image data
-    mimeType::String                          # MIME type (e.g., "image/png")
-end
-
 # ------------------------------------------------------------------------------------------------ #
 #                                            Tool types                                            #
 # ------------------------------------------------------------------------------------------------ #
@@ -158,7 +157,7 @@ A tool available to the agent.
 - `parameters::TParameters`: Tool parameters schema (JSON schema)
 - `execute::Function`: Tool execution function
 - `prepareArguments::Union{Function, Nothing}`: Optional argument preparation callback
-- `parallelExecute::Union{toolparallelExecute, Nothing}`: Override: run tool calls sequentially or in parallel
+- `parallelToolExecute::Bool`: Override: run tool calls sequentially or in parallel
 
 # Returns
 - A new `agentTool` instance
@@ -170,7 +169,7 @@ struct agentTool{TParameters, TDetails}       # A tool available to the agent
     parameters::TParameters                   # Tool parameters schema (JSON schema)
     execute::Function                         # Tool execution function
     prepareArguments::Union{Function, Nothing}  # Optional argument preparation callback
-    parallelExecute::Union{toolparallelExecute, Nothing}  # Override: run tool calls sequentially or in parallel
+    parallelToolExecute::Bool  # Override: run tool calls sequentially or in parallel
 end
 
 
@@ -346,17 +345,6 @@ struct agentToolResult
     terminate::Bool
 end
 
-"""
-Function type for parallel execution override on a tool.
-
-# Arguments
-- Context for parallel execution
-
-# Returns
-- `agentToolCallBatch`: The result batch from parallel execution
-"""
-const toolparallelExecute = Function
-
 """
 Context passed to the `beforeToolCall` hook.