Slack User MCP Server

Instructions

Implementation Reference

• index.ts:423-439 (handler)

  Switch case handler for 'slack_reply_to_thread' tool: validates arguments and invokes slackClient.postReply to execute the reply.

  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:259-276 (helper)

  Core implementation in SlackClient that posts a reply to a thread using Slack's chat.postMessage API with thread_ts parameter.

  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.headers,
      body: JSON.stringify({
        channel: channel_id,
        thread_ts: thread_ts,
        text: text,
        as_user: this.isUserToken
      }),
    });
  
    return response.json();
  }

• index.ts:93-114 (schema)

  Tool definition with name, description, and input schema specifying 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:535-544 (registration)

  Registration of the tool in the list returned by ListToolsRequest handler.

  tools: [
    listChannelsTool,
    postMessageTool,
    replyToThreadTool,
    addReactionTool,
    getChannelHistoryTool,
    getThreadRepliesTool,
    getUsersTool,
    getUserProfileTool,
  ],

• index.ts:22-26 (schema)

  TypeScript interface defining the expected arguments for the slack_reply_to_thread tool.

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