Gmail MCP

Instructions

Implementation Reference

• src/index.ts:1247-1258 (registration)

  Registration of the 'get_smime_info' MCP tool, including inline schema definition and handler function that retrieves S/MIME configuration via Gmail API.

  server.tool("get_smime_info",
    "Gets the specified S/MIME config for the specified send-as alias",
    {
      sendAsEmail: z.string().describe("The email address that appears in the 'From:' header"),
      id: z.string().describe("The immutable ID for the S/MIME config")
    },
    async (params) => {
      return handleTool(config, async (gmail: gmail_v1.Gmail) => {
        const { data } = await gmail.users.settings.sendAs.smimeInfo.get({ userId: 'me', sendAsEmail: params.sendAsEmail, id: params.id })
        return formatResponse(data)
      })
    }

• src/index.ts:1253-1258 (handler)

  Handler function for the get_smime_info tool. It invokes the shared handleTool utility to authenticate, call the Gmail API endpoint for fetching specific S/MIME info, and format the response.

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

• src/index.ts:1249-1252 (schema)

  Zod schema defining input parameters for get_smime_info: sendAsEmail and id.

  {
    sendAsEmail: z.string().describe("The email address that appears in the 'From:' header"),
    id: z.string().describe("The immutable ID for the S/MIME config")
  },

• src/index.ts:50-80 (helper)

  Shared helper function handleTool used by get_smime_info and all other tools for OAuth2 authentication, Gmail client creation, API call execution, and standardized 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) {
      // 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}` });
    }
  }