Gmail MCP Server

Instructions

Implementation Reference

• src/index.ts:1276-1287 (registration)

  Registration of the 'list_smime_info' MCP tool. Defines the input schema (sendAsEmail: string), description, and inline handler function that uses the shared handleTool to authenticate and call the Gmail API's users.settings.sendAs.smimeInfo.list method to retrieve S/MIME configurations for the specified send-as email address.
  server.tool("list_smime_info", "Lists S/MIME configs for the specified send-as alias", { sendAsEmail: z.string().describe("The email address that appears in the 'From:' header") }, async (params) => { return handleTool(config, async (gmail: gmail_v1.Gmail) => { const { data } = await gmail.users.settings.sendAs.smimeInfo.list({ userId: 'me', sendAsEmail: params.sendAsEmail }) return formatResponse(data) }) } )
• src/index.ts:1281-1286 (handler)

  The handler function for the 'list_smime_info' tool. It invokes the shared handleTool utility (which handles OAuth2 authentication and Gmail client creation) and executes the core API call to list S/MIME info.
  async (params) => { return handleTool(config, async (gmail: gmail_v1.Gmail) => { const { data } = await gmail.users.settings.sendAs.smimeInfo.list({ userId: 'me', sendAsEmail: params.sendAsEmail }) return formatResponse(data) }) }
• src/index.ts:1278-1280 (schema)

  Input schema for the 'list_smime_info' tool using Zod: requires 'sendAsEmail' as a string.
  { sendAsEmail: z.string().describe("The email address that appears in the 'From:' header") },
• src/index.ts:50-80 (helper)

  Shared helper function 'handleTool' used by all Gmail tools, including list_smime_info. Manages OAuth2 authentication, validates credentials, creates Gmail client, executes the provided API callback, and handles errors (including auth-specific ones).
  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) { // Check for specific authentication errors if ( error.message?.includes("invalid_grant") || error.message?.includes("refresh_token") || error.message?.includes("invalid_client") || error.message?.includes("unauthorized_client") || error.code === 401 || error.code === 403 ) { return formatResponse({ error: `Authentication failed: ${error.message}. Please re-authenticate by running: npx @shinzolabs/gmail-mcp auth`, }); } return formatResponse({ error: `Tool execution failed: ${error.message}` }); } }
• src/index.ts:48-48 (helper)

  Shared helper 'formatResponse' used by all tools to standardize MCP responses by wrapping the API result in the expected content format.
  const formatResponse = (response: any) => ({ content: [{ type: "text", text: JSON.stringify(response) }] })