Gmail MCP Server

Instructions

Implementation Reference

• src/index.ts:1053-1064 (registration)

  Registration of the 'get_filter' tool, including inline schema and handler function that retrieves a specific Gmail filter by ID using the Gmail API.
  server.tool("get_filter", "Gets a filter", { id: z.string().describe("The ID of the filter to be fetched") }, async (params) => { return handleTool(config, async (gmail: gmail_v1.Gmail) => { const { data } = await gmail.users.settings.filters.get({ userId: 'me', id: params.id }) return formatResponse(data) }) } )
• src/index.ts:1058-1063 (handler)

  Handler function for the get_filter tool. It invokes handleTool with the Gmail API call to users.settings.filters.get to fetch the filter by its ID.
  async (params) => { return handleTool(config, async (gmail: gmail_v1.Gmail) => { const { data } = await gmail.users.settings.filters.get({ userId: 'me', id: params.id }) return formatResponse(data) }) }
• src/index.ts:1055-1057 (schema)

  Input schema for get_filter tool, defining the required 'id' parameter as a string.
  { id: z.string().describe("The ID of the filter to be fetched") },
• src/index.ts:50-80 (helper)

  Shared helper function handleTool used by get_filter (and other tools) to handle OAuth2 authentication, create Gmail client, execute the API call, and format 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) { // 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 get_filter to format the API response as MCP content.
  const formatResponse = (response: any) => ({ content: [{ type: "text", text: JSON.stringify(response) }] })