System message tools duplicates built-in tools when MCP tools present

[shanevcantwell]

Bug

generateToolsSystemMessage() in buildToolsSystemMessage.ts duplicates all built-in tools in the system prompt when any MCP/dynamic tool is present.

Root cause

Line 43 iterates tools (all tools) instead of withDynamicMessage (only tools without systemMessageDescription). When the withDynamicMessage.length > 0 branch fires, every tool — including built-in ones already listed via createSystemMessageExampleCall — gets a second listing via toolToSystemToolDefinition.

Built-in tools appear twice:

1. In the predefined section (via systemMessageDescription.prefix + example call)
2. In the dynamic section (via toolToSystemToolDefinition)

Impact

• Wastes context tokens with duplicate definitions
• Sends contradictory format information (predefined uses example calls, dynamic uses tool_definition blocks)
• Disproportionately affects local models with smaller context windows
• Dormant without MCP tools — only triggers when dynamic tools are registered alongside built-in tools

Fix

One-line change: for (const tool of tools) → for (const tool of withDynamicMessage)

The withDynamicMessage array is already computed on line 18-20 for exactly this purpose.