Function assembleToolPool

source code/tools.ts:347–369

(
  permissionContext: ToolPermissionContext,
  mcpTools: Tools,
)

 * @returns Combined, deduplicated array of built-in and MCP tools
 */
export function assembleToolPool(
  permissionContext: ToolPermissionContext,
  mcpTools: Tools,
): Tools {
  const builtInTools = getTools(permissionContext)

  // Filter out MCP tools that are in the deny list
  const allowedMcpTools = filterToolsByDenyRules(mcpTools, permissionContext)

  // Sort each partition for prompt-cache stability, keeping built-ins as a
  // contiguous prefix. The server's claude_code_system_cache_policy places a
  // global cache breakpoint after the last prefix-matched built-in tool; a flat
  // sort would interleave MCP tools into built-ins and invalidate all downstream
  // cache keys whenever an MCP tool sorts between existing built-ins. uniqBy
  // preserves insertion order, so built-ins win on name conflict.
  // Avoid Array.toSorted (Node 20+) — we support Node 18. builtInTools is
  // readonly so copy-then-sort; allowedMcpTools is a fresh .filter() result.
  const byName = (a: Tool, b: Tool) => a.name.localeCompare(b.name)
  return uniqBy(
    [...builtInTools].sort(byName).concat(allowedMcpTools.sort(byName)),
    'name',
  )
}

/**
 * Get all tools including both built-in tools and MCP tools.