Retrieve all replies in a Slack thread using the parent message's timestamp, or filter to only replies newer than a specified timestamp for incremental fetches.
スレッドの返信を取得する。親メッセージの ts を渡す。oldest を渡すと、それより新しい返信だけ返す（親も含めない）。oldest を渡さない場合は親メッセージを含めて全件返す（ページ送りで最大 2000 件）。
| Name | Required | Description | Default |
|---|---|---|---|
| oldest | No | この ts より新しい返信だけ返す（前回見た latest_reply を渡す） | |
| threadTs | Yes | 親メッセージの ts | |
| channelId | Yes | チャンネル ID |
Changes observed during successful MCP inspections.
v0.3.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description carries the burden of behavioral disclosure. It explains the pagination behavior (max 2000 replies, inclusion/exclusion of parent message) which is useful, but doesn't disclose rate limits, error conditions, or what happens with empty threads. The behavior described is consistent with the tool's purpose.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is compact and front-loaded with the core purpose, then explains the two modes of operation. Every sentence adds value, though the pagination details could be slightly more structured.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a read-only retrieval tool with 100% schema coverage, the description covers the essential behavior. However, it doesn't mention return format, sorting order, or error handling, which an agent might need to know for correct invocation. The lack of an output schema increases the burden on the description to explain what the caller receives.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, so the schema already documents all three parameters. The description adds context about the oldest parameter's role in pagination and the parent message inclusion behavior, but doesn't add significant meaning beyond the schema's parameter descriptions.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the tool retrieves thread replies and requires the parent message's ts. It distinguishes itself from siblings by focusing on thread replies rather than channel history or active threads, though it doesn't explicitly name a sibling alternative.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description explains when to use the oldest parameter and the default behavior when it's omitted, giving clear context for pagination. It doesn't explicitly state when not to use this tool versus alternatives, but the thread-specific focus makes the usage context clear.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.