Gmail MCP

Instructions

Implementation Reference

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

  Registration of the 'delete_filter' MCP tool, including schema (id: string) and handler function that authenticates via handleTool and calls 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:1045-1051 (handler)

  Handler function for 'delete_filter' tool: uses shared handleTool for auth and Gmail client creation, then deletes the specified filter using gmail.users.settings.filters.delete.

    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 'delete_filter' tool: requires 'id' as string, the ID of the filter to delete.

  {
    id: z.string().describe("The ID of the filter to be deleted")
  },

• src/index.ts:50-80 (helper)

  Shared helper function 'handleTool' used by 'delete_filter' (and other tools) for OAuth2 authentication, Gmail client creation/validation, API call execution, and 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}` });
    }
  }