Gmail MCP Server

Instructions

Implementation Reference

• src/index.ts:467-476 (registration)

  Registration of the 'list_labels' MCP tool, including empty input schema and handler function that uses the Gmail API to list all labels via handleTool helper.
  server.tool("list_labels", "List all labels in the user's mailbox", {}, async () => { return handleTool(config, async (gmail: gmail_v1.Gmail) => { const { data } = await gmail.users.labels.list({ userId: 'me' }) return formatResponse(data) }) } )
• src/index.ts:470-475 (handler)

  Handler function for list_labels tool that authenticates via handleTool and calls Gmail users.labels.list API.
  async () => { return handleTool(config, async (gmail: gmail_v1.Gmail) => { const { data } = await gmail.users.labels.list({ userId: 'me' }) return formatResponse(data) }) }
• src/index.ts:50-66 (helper)

  Shared helper function used by list_labels (and other tools) to handle OAuth2 validation and Gmail client creation before executing the API call.
  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)

  Helper function to format API responses for MCP tools.
  const formatResponse = (response: any) => ({ content: [{ type: "text", text: JSON.stringify(response) }] })