MCP Complete Implementation Guide

Instructions

Implementation Reference

• server.js:232-246 (handler)

  The writeFile handler method executes the write_file tool logic: writes content to the specified file path using fs.writeFileSync equivalent (promises), handles errors, and returns MCP-formatted TextContent success message.

  async writeFile(filePath, content) {
    try {
      await fs.writeFile(filePath, content, 'utf-8');
      return {
        content: [
          {
            type: 'text',
            text: `Successfully wrote to ${filePath}`,
          },
        ],
      };
    } catch (error) {
      throw new Error(`Failed to write file: ${error.message}`);
    }
  }

• server.js:58-75 (schema)

  The input schema definition for the write_file tool, registered in the ListToolsRequestSchema handler, specifying path and content as required string parameters.

  {
    name: 'write_file',
    description: 'Write content to a file',
    inputSchema: {
      type: 'object',
      properties: {
        path: {
          type: 'string',
          description: 'The path to the file to write',
        },
        content: {
          type: 'string',
          description: 'The content to write to the file',
        },
      },
      required: ['path', 'content'],
    },
  },

• server.py:208-217 (handler)

  The write_file handler method executes the tool logic: creates parent directories if needed, writes content using Path.write_text, returns MCP TextContent success or raises error.

  async def write_file(self, file_path: str, content: str) -> list[types.TextContent]:
      """Write content to file"""
      try:
          path = Path(file_path)
          path.parent.mkdir(parents=True, exist_ok=True)
          path.write_text(content, encoding="utf-8")
          return [types.TextContent(type="text", text=f"Successfully wrote to {file_path}")]
      except Exception as error:
          raise Exception(f"Failed to write file: {str(error)}")

• server.py:86-103 (schema)

  The Tool object definition for write_file including inputSchema, used in the list_tools handler for registration.

  types.Tool(
      name="write_file",
      description="Write content to a file",
      inputSchema={
          "type": "object",
          "properties": {
              "path": {
                  "type": "string",
                  "description": "The path to the file to write",
              },
              "content": {
                  "type": "string",
                  "description": "The content to write to the file",
              },
          },
          "required": ["path", "content"],
      },
  ),

• chatgpt-proxy.js:225-227 (handler)

  Direct implementation of write_file in the OpenAI proxy's tool execution switch, using fs.writeFile and returning success object.

  case 'write_file':
    await fs.writeFile(args.path, args.content, 'utf-8');
    return { success: true, message: `Successfully wrote to ${args.path}` };