Gmail MCP Server

Instructions

Implementation Reference

• src/index.ts:1040-1051 (registration)

  Registration of the 'delete_filter' MCP tool, including inline handler and schema definition. The handler uses handleTool to authenticate and call Gmail API to delete the filter by ID.
  server.tool("delete_filter", "Deletes a filter", { id: z.string().describe("The ID of the filter to be deleted") }, async (params) => { return handleTool(config, async (gmail: gmail_v1.Gmail) => { const { data } = await gmail.users.settings.filters.delete({ userId: 'me', id: params.id }) return formatResponse(data) }) } )
• src/index.ts:1045-1050 (handler)

  Handler function that executes the tool logic: invokes handleTool with config and an inner async function that deletes the filter using Gmail API.
  async (params) => { return handleTool(config, async (gmail: gmail_v1.Gmail) => { const { data } = await gmail.users.settings.filters.delete({ userId: 'me', id: params.id }) return formatResponse(data) }) }
• src/index.ts:1042-1044 (schema)

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

  Shared helper function handleTool that manages OAuth2 authentication, validates credentials, creates Gmail client, executes the provided API call, and handles errors including auth failures.
  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)

  Helper function to format tool responses as MCP content blocks with JSON stringified data.
  const formatResponse = (response: any) => ({ content: [{ type: "text", text: JSON.stringify(response) }] })