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

Annotations only cover the safety profile (readOnlyHint=false, destructiveHint=false, openWorldHint=true, idempotentHint=false); the description adds real behavioral context: credential-bearing content is refused, the text is visible to other members, the 4000-character cap, and precisely why idempotentHint is false (only retries with the same key are free, otherwise each call creates a new comment). This is disclosure beyond the structured fields, and it is consistent with the annotations.

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?

Front-loaded with the action and target, then limits, idempotency, and side effects — no filler sentences. However, it is a single long run-on and the clause 'Returns the comment and replayed.' is garbled and hard to parse, costing some clarity.

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?

With full schema coverage, annotations, and an output schema, the description only needs to carry intent, constraints, and side effects — which it largely does (size limit, credential refusal, visibility, idempotent retry). Missing only failure-mode context (nonexistent task, missing agent, permission errors), so not a 5.

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 coverage is 100%, so the baseline is 3; the description goes further by explaining the behavioral meaning of idempotency_key (same key returns the same comment) rather than restating the schema's 'a retry with the same key is free,' and reinforces the body length bound. It adds little on agent_id or room_id, hence not a 5.

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?

Specific verb+resource (add a comment to a task's discussion thread) with a scope qualifier that separates it from the sibling city_room_post: comments 'stay on the task and are not posted in the room thread.' An agent can route between task comments and room posts without opening either schema.

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 'not posted in the room thread' clause gives an implicit when-to-use/where-not signal against city_room_post, and the idempotency-key sentence tells the agent when to supply a key (retry-safe calls). It does not explicitly name the alternative tool or state prerequisites (e.g. membership/permissions), so it stops short of full routing guidance.

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