Charles MCP Server

Instructions

Implementation Reference

• charles_mcp/tools/reset.py:27-56 (handler)

  The `throttling` tool implementation that handles the input, validates the preset, and calls the Charles client.

  async def throttling(ctx: ToolContext, preset: ThrottlingPreset) -> str:
      """Set a network throttling preset in Charles."""
      logger.info("Tool called: throttling(preset=%s)", preset)
      deps = get_tool_dependencies(ctx)
  
      preset_clean = preset.strip()
      if not preset_clean:
          return (
              "Error: parameter `preset` cannot be empty. "
              "Use one of the supported presets, for example: 3G / 4G / 5G / off / deactivate."
          )
  
      preset_lower = preset_clean.lower()
      supported = {value.lower() for value in THROTTLING_PRESET_CHOICES}
      if preset_lower not in supported:
          return (
              "Error: parameter `preset` is invalid. "
              f"Supported values: {', '.join(THROTTLING_PRESET_CHOICES)}. "
              'Retry with something like throttling("3G") or throttling("off").'
          )
  
      normalized_preset = "3G" if preset_lower in ("start", "on") else preset_clean
  
      try:
          async with deps.client_factory(deps.config) as client:
              success, message = await client.set_throttling(normalized_preset)
              return f"{'Success' if success else 'Error'}: {message}"
      except CharlesClientError as exc:
          logger.error("Throttling error: %s", exc)
          return f"Error: {exc}"

• charles_mcp/tools/reset.py:26-27 (registration)

  The MCP tool decorator registration for `throttling`.

  @mcp.tool()
  async def throttling(ctx: ToolContext, preset: ThrottlingPreset) -> str:

• charles_mcp/tools/tool_contract.py:120-130 (schema)

  The `ThrottlingPreset` type definition used for input validation in the throttling tool.

  ThrottlingPreset = Annotated[
      str,
      Field(
          description=(
              "弱网预设名称。"
              "仅允许固定值：3G/4G/5G/fibre/100mbps/56k/256k/deactivate/off/on/start。"
          ),
          json_schema_extra={"enum": list(THROTTLING_PRESET_CHOICES)},
      ),
  ]