Read a single comment thread's messages

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

The readOnlyHint annotation already declares this as a read operation. The description adds valuable context beyond the annotation by detailing the returned content (full message history with authors and timestamps), which is especially useful given no output schema. No contradiction exists.

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 two concise sentences with no unnecessary fluff. It front-loads the core function and then provides a usage tip, making every sentence earn its place.

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 simple read-only tool with one parameter, the description covers the function, the return contents, and the trigger condition for use. It does not mention error handling or edge cases, but these are not essential for this straightforward operation given the annotations.

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?

The schema fully describes the single parameter thread_id with a clear explanation. The description reinforces the source of the ID (from list_comments) but does not add substantial semantic value beyond the schema, so the baseline of 3 is appropriate.

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 fetches the full message history of one thread, specifying the resource and scope ('all replies with author + timestamp'). It also distinguishes itself from the sibling list_comments tool by indicating this is for reading a specific thread after discovery.

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 explicitly says 'Use this when `list_comments` shows a thread that looks relevant', providing a clear when-to-use scenario. It does not explicitly name alternatives or exclusion conditions, but the context of sibling tools implies the distinction.

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