Frappe MCP Server

Instructions

    Execute a whitelisted Frappe method.
    
    Args:
        method: Method name to call (whitelisted)
        params: Parameters to pass to the method (optional)
    

Implementation Reference

• src/tools/documents.py:417-446 (handler)

  The core handler function for the 'call_method' tool. It is decorated with @mcp.tool() for automatic registration and implements calling whitelisted Frappe methods via the /api/method endpoint, with proper error handling using a shared helper.

  @mcp.tool()
  async def call_method(
      method: str,
      params: Optional[Dict[str, Any]] = None
  ) -> str:
      """
      Execute a whitelisted Frappe method.
      
      Args:
          method: Method name to call (whitelisted)
          params: Parameters to pass to the method (optional)
      """
      try:
          client = get_client()
          
          # Prepare request data
          request_data = {"cmd": method}
          if params:
              request_data.update(params)
          
          # Make API request to call method
          response = await client.post("api/method", json_data=request_data)
          
          if "message" in response:
              return json.dumps(response["message"], indent=2)
          else:
              return json.dumps(response, indent=2)
              
      except Exception as error:
          return _format_error_response(error, "call_method")

• src/server.py:40-40 (registration)

  Invocation of documents.register_tools(mcp) in the main server setup, which triggers the registration of the 'call_method' tool (and other document tools) with the MCP server instance.

  documents.register_tools(mcp)

• src/tools/documents.py:51-78 (helper)

  Helper function used by call_method (and other tools) to format detailed error responses, including credential checks and Frappe-specific error handling.

  def _format_error_response(error: Exception, operation: str) -> str:
      """Format error response with detailed information."""
      credentials_check = validate_api_credentials()
      
      # Build diagnostic information
      diagnostics = [
          f"Error in {operation}",
          f"Error type: {type(error).__name__}",
          f"Is FrappeApiError: {isinstance(error, FrappeApiError)}",
          f"API Key available: {credentials_check['details']['api_key_available']}",
          f"API Secret available: {credentials_check['details']['api_secret_available']}"
      ]
      
      # Check for missing credentials first
      if not credentials_check["valid"]:
          error_msg = f"Authentication failed: {credentials_check['message']}. "
          error_msg += "API key/secret is the only supported authentication method."
          return error_msg
      
      # Handle FrappeApiError
      if isinstance(error, FrappeApiError):
          error_msg = f"Frappe API error: {error}"
          if error.status_code in (401, 403):
              error_msg += " Please check your API key and secret."
          return error_msg
      
      # Default error handling
      return f"Error in {operation}: {str(error)}"