Gmail MCP

Instructions

Implementation Reference

• src/index.ts:1182-1198 (registration)

  Registration of the 'patch_send_as' tool, including description, input schema, and inline handler function that updates a send-as alias via Gmail API patch call.

  server.tool("patch_send_as",
    "Patches the specified send-as alias",
    {
      sendAsEmail: z.string().describe("The send-as alias to be updated"),
      displayName: z.string().optional().describe("A name that appears in the 'From:' header"),
      replyToAddress: z.string().optional().describe("An optional email address that is included in a 'Reply-To:' header"),
      signature: z.string().optional().describe("An optional HTML signature"),
      isPrimary: z.boolean().optional().describe("Whether this address is the primary address"),
      treatAsAlias: z.boolean().optional().describe("Whether Gmail should treat this address as an alias")
    },
    async (params) => {
      const { sendAsEmail, ...patchData } = params
      return handleTool(config, async (gmail: gmail_v1.Gmail) => {
        const { data } = await gmail.users.settings.sendAs.patch({ userId: 'me', sendAsEmail, requestBody: patchData })
        return formatResponse(data)
      })
    }

• src/index.ts:1192-1198 (handler)

  The handler function for 'patch_send_as' tool. Destructures params to separate sendAsEmail and patch data, then uses handleTool helper to call Gmail API's users.settings.sendAs.patch.

  async (params) => {
    const { sendAsEmail, ...patchData } = params
    return handleTool(config, async (gmail: gmail_v1.Gmail) => {
      const { data } = await gmail.users.settings.sendAs.patch({ userId: 'me', sendAsEmail, requestBody: patchData })
      return formatResponse(data)
    })
  }

• src/index.ts:1184-1191 (schema)

  Zod input schema for the 'patch_send_as' tool, defining required sendAsEmail and optional fields for updating the send-as alias.

  {
    sendAsEmail: z.string().describe("The send-as alias to be updated"),
    displayName: z.string().optional().describe("A name that appears in the 'From:' header"),
    replyToAddress: z.string().optional().describe("An optional email address that is included in a 'Reply-To:' header"),
    signature: z.string().optional().describe("An optional HTML signature"),
    isPrimary: z.boolean().optional().describe("Whether this address is the primary address"),
    treatAsAlias: z.boolean().optional().describe("Whether Gmail should treat this address as an alias")
  },

• src/index.ts:50-80 (helper)

  Generic helper function used by 'patch_send_as' (and other tools) to handle OAuth2 authentication, Gmail client creation, API call execution, and error handling with specific auth error responses.

  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}` });
    }
  }