Gmail MCP

Instructions

Implementation Reference

• src/index.ts:676-687 (registration)

  Registers the 'trash_message' MCP tool with the server, including description, input schema requiring a message ID, and the handler function.

  server.tool("trash_message",
    "Move a message to the trash",
    {
      id: z.string().describe("The ID of the message to move to trash")
    },
    async (params) => {
      return handleTool(config, async (gmail: gmail_v1.Gmail) => {
        const { data } = await gmail.users.messages.trash({ userId: 'me', id: params.id })
        return formatResponse(data)
      })
    }
  )

• src/index.ts:681-686 (handler)

  The handler function that executes the tool logic: authenticates via handleTool, calls Gmail API users.messages.trash with the provided message ID, and formats the response.

  async (params) => {
    return handleTool(config, async (gmail: gmail_v1.Gmail) => {
      const { data } = await gmail.users.messages.trash({ userId: 'me', id: params.id })
      return formatResponse(data)
    })
  }

• src/index.ts:678-680 (schema)

  Input schema for the tool: requires a string 'id' parameter, the Gmail message ID.

  {
    id: z.string().describe("The ID of the message to move to trash")
  },

• src/index.ts:50-80 (helper)

  Shared helper function used by all Gmail tools to handle OAuth2 authentication, client creation, API call execution, and error handling (including auth-specific 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)

  Helper function to format API responses into MCP-compatible content structure.

  const formatResponse = (response: any) => ({ content: [{ type: "text", text: JSON.stringify(response) }] })