Gmail MCP Server

Instructions

Implementation Reference

• src/index.ts:454-465 (registration)

  Registers the MCP tool 'get_label' with input schema (id: string) and inline handler. The handler uses the shared 'handleTool' utility to authenticate, create a Gmail client, and call gmail.users.labels.get to retrieve the label by ID, then formats the response.

  server.tool("get_label",
    "Get a specific label by ID",
    {
      id: z.string().describe("The ID of the label to retrieve")
    },
    async (params) => {
      return handleTool(config, async (gmail: gmail_v1.Gmail) => {
        const { data } = await gmail.users.labels.get({ userId: 'me', id: params.id })
        return formatResponse(data)
      })
    }
  )

• src/index.ts:459-464 (handler)

  The inline handler function for the 'get_label' tool, which delegates to 'handleTool' for auth and API execution.

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

• src/index.ts:456-458 (schema)

  Input schema for 'get_label' tool using Zod: requires 'id' as string.

  {
    id: z.string().describe("The ID of the label to retrieve")
  },

• src/index.ts:50-66 (helper)

  Shared helper 'handleTool' used by 'get_label' and other tools to manage OAuth2 authentication, validate credentials, instantiate Gmail client, execute the provided API callback, and handle errors.

  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:48-48 (helper)

  Utility to format API responses for MCP tools, used by 'get_label' handler.

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