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larrygmaguire-hash

Slack Note Capture MCP Server

slack_post_to_thread

Post replies to existing Slack message threads to continue conversations and maintain organized discussions within channels.

Instructions

Post a reply to an existing message thread. Use this to continue a conversation in a thread.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
channel_idNoThe Slack channel ID. Defaults to configured inbox channel.
thread_tsYesThe timestamp of the parent message to reply to.
textYesThe message text to post.

Implementation Reference

  • Handler implementation for slack_post_to_thread which posts a message to a specific Slack thread.
    case "slack_post_to_thread": {
      const channelId = args.channel_id || DEFAULT_CHANNEL;
      const threadTs = args.thread_ts;
      const text = args.text;
    
      if (!channelId) {
        return {
          content: [
            {
              type: "text",
              text: "Error: No channel ID provided and no default channel configured.",
            },
          ],
        };
      }
    
      const result = await slack.chat.postMessage({
        channel: channelId,
        text: text,
        thread_ts: threadTs,
      });
    
      return {
        content: [
          {
            type: "text",
            text: JSON.stringify(
              {
  • src/index.js:117-140 (registration)
    Registration of the slack_post_to_thread tool with its input schema.
    {
      name: "slack_post_to_thread",
      description:
        "Post a reply to an existing message thread. Use this to continue a conversation in a thread.",
      inputSchema: {
        type: "object",
        properties: {
          channel_id: {
            type: "string",
            description:
              "The Slack channel ID. Defaults to configured inbox channel.",
          },
          thread_ts: {
            type: "string",
            description: "The timestamp of the parent message to reply to.",
          },
          text: {
            type: "string",
            description: "The message text to post.",
          },
        },
        required: ["thread_ts", "text"],
      },
    },
Behavior2/5

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

No annotations provided, so description carries full burden. Verb 'Post' implies write operation, but lacks disclosure of side effects (visibility, notification triggers), error conditions (invalid thread_ts), rate limits, or return value behavior.

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

Conciseness4/5

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

Two sentences, front-loaded with the core action. Slightly redundant ('thread' concept repeated in both sentences), but no major waste. Appropriate length for the tool's complexity.

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

Completeness3/5

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

Adequate for a 3-parameter messaging tool with complete schema coverage, but gaps remain: no mention of message visibility (public vs private), error handling for invalid timestamps, or required auth scopes. No output schema exists, yet description doesn't clarify what indicates success.

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 has 100% description coverage with clear field definitions. Description adds semantic framing ('reply to an existing message thread') that reinforces thread_ts relationship, but doesn't add syntax details, format requirements, or validation rules beyond the schema.

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?

States specific action (Post a reply) and resource (existing message thread) clearly. Mentions 'thread' twice, implicitly distinguishing from sibling slack_post_message, but doesn't explicitly reference the sibling or clarify when to use each tool.

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

Usage Guidelines3/5

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

Provides implied usage guidance ('Use this to continue a conversation in a thread'), suggesting conversational context. However, lacks explicit when/when-not guidance or explicit comparison to slack_post_message for top-level vs threaded messages.

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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