MCP Server for Slack

Instructions

Implementation Reference

• index.ts:449-465 (handler)

  Executes the slack_reply_to_thread tool by validating input arguments and invoking the SlackClient.postReply method to send the reply via Slack API.

  case "slack_reply_to_thread": {
    const args = request.params
      .arguments as unknown as ReplyToThreadArgs;
    if (!args.channel_id || !args.thread_ts || !args.text) {
      throw new Error(
        "Missing required arguments: channel_id, thread_ts, and text",
      );
    }
    const response = await slackClient.postReply(
      args.channel_id,
      args.thread_ts,
      args.text,
    );
    return {
      content: [{ type: "text", text: JSON.stringify(response) }],
    };
  }

• index.ts:93-114 (schema)

  Defines the Tool object for slack_reply_to_thread, including name, description, and input schema with required parameters: channel_id, thread_ts, text.

  const replyToThreadTool: Tool = {
    name: "slack_reply_to_thread",
    description: "Reply to a specific message thread in Slack",
    inputSchema: {
      type: "object",
      properties: {
        channel_id: {
          type: "string",
          description: "The ID of the channel containing the thread",
        },
        thread_ts: {
          type: "string",
          description: "The timestamp of the parent message in the format '1234567890.123456'. Timestamps in the format without the period can be converted by adding the period such that 6 numbers come after it.",
        },
        text: {
          type: "string",
          description: "The reply text",
        },
      },
      required: ["channel_id", "thread_ts", "text"],
    },
  };

• index.ts:286-302 (helper)

  SlackClient method that makes the HTTP POST request to Slack's chat.postMessage API to reply to a thread, using the provided channel_id, thread_ts, and text.

  async postReply(
    channel_id: string,
    thread_ts: string,
    text: string,
  ): Promise<any> {
    const response = await fetch("https://slack.com/api/chat.postMessage", {
      method: "POST",
      headers: this.botHeaders,
      body: JSON.stringify({
        channel: channel_id,
        thread_ts: thread_ts,
        text: text,
      }),
    });
  
    return response.json();
  }

• index.ts:567-582 (registration)

  Registers the slack_reply_to_thread tool (as replyToThreadTool) in the list of available tools returned by the ListToolsRequest handler.

  server.setRequestHandler(ListToolsRequestSchema, async () => {
    console.log("Received ListToolsRequest");
    return {
      tools: [
        listChannelsTool,
        postMessageTool,
        replyToThreadTool,
        addReactionTool,
        getChannelHistoryTool,
        getThreadRepliesTool,
        getUsersTool,
        getUserProfileTool,
        lookupUserByEmailTool,
      ],
    };
  });

• index.ts:22-26 (schema)

  TypeScript interface defining the input arguments for the slack_reply_to_thread tool, used for type checking in the handler.

  interface ReplyToThreadArgs {
    channel_id: string;
    thread_ts: string;
    text: string;
  }