list_threads

Instructions

Implementation Reference

• src/index.ts:739-773 (registration)

  Registers the 'list_threads' MCP tool with description, input schema using Zod, and inline handler function that calls Gmail API to list threads.

  server.tool("list_threads",
    "List threads in the user's mailbox",
    {
      maxResults: z.number().optional().describe("Maximum number of threads to return"),
      pageToken: z.string().optional().describe("Page token to retrieve a specific page of results"),
      q: z.string().optional().describe("Only return threads matching the specified query"),
      labelIds: z.array(z.string()).optional().describe("Only return threads with labels that match all of the specified label IDs"),
      includeSpamTrash: z.boolean().optional().describe("Include threads from SPAM and TRASH in the results"),
      includeBodyHtml: z.boolean().optional().describe("Whether to include the parsed HTML in the return for each body, excluded by default because they can be excessively large"),
    },
    async (params) => {
      return handleTool(config, async (gmail: gmail_v1.Gmail) => {
        const { data } = await gmail.users.threads.list({ userId: 'me', ...params })
  
        if (data.threads) {
          data.threads = data.threads.map(thread => {
            if (thread.messages) {
              thread.messages = thread.messages.map(message => {
                if (message.payload) {
                  message.payload = processMessagePart(
                    message.payload,
                    params.includeBodyHtml
                  )
                }
                return message
              })
            }
            return thread
          })
        }
  
        return formatResponse(data)
      })
    }
  )

• src/index.ts:749-772 (handler)

  The handler function for 'list_threads' tool. It invokes handleTool which authenticates, calls gmail.users.threads.list with params, optionally decodes and processes message payloads using processMessagePart, and returns formatted JSON response.

  async (params) => {
    return handleTool(config, async (gmail: gmail_v1.Gmail) => {
      const { data } = await gmail.users.threads.list({ userId: 'me', ...params })
  
      if (data.threads) {
        data.threads = data.threads.map(thread => {
          if (thread.messages) {
            thread.messages = thread.messages.map(message => {
              if (message.payload) {
                message.payload = processMessagePart(
                  message.payload,
                  params.includeBodyHtml
                )
              }
              return message
            })
          }
          return thread
        })
      }
  
      return formatResponse(data)
    })
  }

• src/index.ts:742-748 (schema)

  Zod input schema for 'list_threads' tool parameters, validating optional filters like maxResults, query (q), labels, etc.

    maxResults: z.number().optional().describe("Maximum number of threads to return"),
    pageToken: z.string().optional().describe("Page token to retrieve a specific page of results"),
    q: z.string().optional().describe("Only return threads matching the specified query"),
    labelIds: z.array(z.string()).optional().describe("Only return threads with labels that match all of the specified label IDs"),
    includeSpamTrash: z.boolean().optional().describe("Include threads from SPAM and TRASH in the results"),
    includeBodyHtml: z.boolean().optional().describe("Whether to include the parsed HTML in the return for each body, excluded by default because they can be excessively large"),
  },

• src/index.ts:50-66 (helper)

  Shared helper function used by 'list_threads' (and other tools) to handle OAuth2 authentication, create Gmail client, execute the API call, and catch 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) {
      return `Tool execution failed: ${error.message}`
    }
  }

• src/index.ts:80-94 (helper)

  Helper to recursively decode base64 bodies (except HTML unless specified), filter headers, used in 'list_threads' to process thread message payloads.

  const processMessagePart = (messagePart: MessagePart, includeBodyHtml = false): MessagePart => {
    if ((messagePart.mimeType !== 'text/html' || includeBodyHtml) && messagePart.body) {
      messagePart.body = decodedBody(messagePart.body)
    }
  
    if (messagePart.parts) {
      messagePart.parts = messagePart.parts.map(part => processMessagePart(part, includeBodyHtml))
    }
  
    if (messagePart.headers) {
      messagePart.headers = messagePart.headers.filter(header => RESPONSE_HEADERS_LIST.includes(header.name || ''))
    }
  
    return messagePart
  }