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lars-hagen

Slack User MCP Server

by lars-hagen

slack_get_thread_replies

Retrieve all replies from a Slack message thread by providing the channel ID and parent message timestamp to access threaded conversations.

Instructions

Get all replies in a message thread

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
channel_idYesThe ID of the channel containing the thread
thread_tsYesThe 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.

Implementation Reference

  • Core handler implementation that calls the Slack conversations.replies API to retrieve 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.headers },
      );
    
      return response.json();
    }
  • Tool metadata and input schema definition for slack_get_thread_replies.
    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"],
      },
    };
  • TypeScript interface defining the input arguments for the tool.
    interface GetThreadRepliesArgs {
      channel_id: string;
      thread_ts: string;
    }
  • index.ts:473-488 (registration)
    Dispatch case in CallToolRequest handler that invokes the getThreadReplies method.
    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:534-543 (registration)
    Tool list registration in ListToolsRequest handler, including slack_get_thread_replies.
    return {
      tools: [
        listChannelsTool,
        postMessageTool,
        replyToThreadTool,
        addReactionTool,
        getChannelHistoryTool,
        getThreadRepliesTool,
        getUsersTool,
        getUserProfileTool,
Behavior2/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description carries the full burden of behavioral disclosure. It states 'Get all replies' but does not specify if this is a read-only operation, requires authentication, has rate limits, or describes the return format (e.g., list of messages). For a tool with zero annotation coverage, this is a significant gap in transparency.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, efficient sentence that directly states the tool's purpose without any unnecessary words. It is front-loaded and wastes no space, making it highly concise and well-structured for quick understanding.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the complexity of a Slack API tool with no annotations and no output schema, the description is incomplete. It lacks details on behavioral traits (e.g., read-only status, authentication needs), return values, and usage context. For a tool that retrieves data, more information is needed to be fully helpful to an AI agent.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, with clear descriptions for both parameters (channel_id and thread_ts). The description does not add any meaning beyond what the schema provides, such as explaining how to obtain these IDs or the thread_ts format in practice. Baseline 3 is appropriate when the schema handles parameter documentation adequately.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the verb 'Get' and the resource 'all replies in a message thread', making the purpose specific and understandable. However, it does not explicitly differentiate from sibling tools like 'slack_reply_to_thread' or 'slack_get_channel_history', which might also involve thread interactions or message retrieval, so it lacks sibling differentiation for a perfect score.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides no guidance on when to use this tool versus alternatives. It does not mention prerequisites, such as needing a valid channel ID and thread timestamp, or compare it to siblings like 'slack_get_channel_history' for broader message retrieval, leaving usage context implied at best.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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