Gmail MCP

Instructions

Implementation Reference

• src/index.ts:643-654 (registration)

  Registration of the trash_message tool using McpServer.tool, defining its name, description, input schema (message ID), and inline handler function that uses the Gmail API to move the message to trash.

  server.tool("trash_message",
    "Move a message to the trash",
    {
      id: z.string().describe("The ID of the message to move to trash")
    },
    async (params) => {
      return handleTool(config, async (gmail: gmail_v1.Gmail) => {
        const { data } = await gmail.users.messages.trash({ userId: 'me', id: params.id })
        return formatResponse(data)
      })
    }
  )

• src/index.ts:648-653 (handler)

  The handler function for trash_message tool, which invokes handleTool to authenticate and call gmail.users.messages.trash API with the provided message ID.

  async (params) => {
    return handleTool(config, async (gmail: gmail_v1.Gmail) => {
      const { data } = await gmail.users.messages.trash({ userId: 'me', id: params.id })
      return formatResponse(data)
    })
  }

• src/index.ts:645-647 (schema)

  Input schema for trash_message tool using Zod: requires a string 'id' parameter for the message ID.

  {
    id: z.string().describe("The ID of the message to move to trash")
  },

• src/index.ts:49-65 (helper)

  Shared helper function handleTool used by trash_message (and other tools) to manage OAuth2 authentication, credential validation, Gmail client creation, and API call execution with error handling.

  const handleTool = async (queryConfig: Record<string, any> | undefined, apiCall: (gmail: gmail_v1.Gmail) => Promise<any>) => {
    try {
      const oauth2Client = queryConfig ? createOAuth2Client(queryConfig) : defaultOAuth2Client
      if (!oauth2Client) throw new Error('OAuth2 client could not be created, please check your credentials')
  
      const credentialsAreValid = await validateCredentials(oauth2Client)
      if (!credentialsAreValid) throw new Error('OAuth2 credentials are invalid, please re-authenticate')
  
      const gmailClient = queryConfig ? google.gmail({ version: 'v1', auth: oauth2Client }) : defaultGmailClient
      if (!gmailClient) throw new Error('Gmail client could not be created, please check your credentials')
  
      const result = await apiCall(gmailClient)
      return result
    } catch (error: any) {
      return `Tool execution failed: ${error.message}`
    }
  }

• src/index.ts:47-48 (helper)

  Helper function formatResponse used to standardize tool responses into MCP content format by JSON stringifying the API response.

  const formatResponse = (response: any) => ({ content: [{ type: "text", text: JSON.stringify(response) }] })