Gmail MCP Server

Instructions

Implementation Reference

• src/index.ts:371-386 (handler)

  The complete implementation of the 'send_draft' tool, including registration, schema, and handler logic. The handler uses the Gmail API to send a draft by ID, with error handling for common issues like missing recipients.
  server.tool("send_draft", "Send an existing draft", { id: z.string().describe("The ID of the draft to send") }, async (params) => { return handleTool(config, async (gmail: gmail_v1.Gmail) => { try { const { data } = await gmail.users.drafts.send({ userId: 'me', requestBody: { id: params.id } }) return formatResponse(data) } catch (error) { return formatResponse({ error: 'Error sending draft, are you sure you have at least one recipient?' }) } }) } )
• src/index.ts:373-375 (schema)

  Input schema for the send_draft tool requiring a draft ID.
  { id: z.string().describe("The ID of the draft to send") },
• src/index.ts:50-80 (helper)

  General helper function used by send_draft (and other tools) to handle OAuth2 authentication, client creation, and API call execution with 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}` }); } }
• src/index.ts:48-49 (helper)

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