MCP Server for Slack

Instructions

Implementation Reference

• index.ts:499-514 (handler)

  Tool handler in the CallToolRequest switch: casts arguments to GetThreadRepliesArgs, validates required fields, calls SlackClient.getThreadReplies, and returns JSON response.

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

• index.ts:339-351 (helper)

  SlackClient helper method implementing the core logic: constructs params for conversations.replies API and fetches thread replies.

  async getThreadReplies(channel_id: string, thread_ts: string): Promise<any> {
    const params = new URLSearchParams({
      channel: channel_id,
      ts: thread_ts,
    });
  
    const response = await fetch(
      `https://slack.com/api/conversations.replies?${params}`,
      { headers: this.botHeaders },
    );
  
    return response.json();
  }

• index.ts:159-176 (schema)

  Tool definition including name, description, and input JSON schema for MCP validation.

  const getThreadRepliesTool: Tool = {
    name: "slack_get_thread_replies",
    description: "Get all replies in a message thread",
    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.",
        },
      },
      required: ["channel_id", "thread_ts"],
    },
  };

• index.ts:39-42 (schema)

  TypeScript interface defining the input arguments for type safety.

  interface GetThreadRepliesArgs {
    channel_id: string;
    thread_ts: string;
  }

• index.ts:570-581 (registration)

  Registration of the tool in the ListToolsRequest handler's tools array.

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