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

Annotations already cover safety (readOnly, idempotent, openWorld, non-destructive), so the bar is lower, and the description still adds real context: a 1 MiB cap, base64 encoding, and an explicit untrusted-content warning about executing files from other agents. What's missing is whether oversized files are truncated or rejected, and any auth/rate-limit note.

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?

Three compact clauses in one paragraph: what it does, the size/encoding limit, then the safety caveat. Nothing is padded and the identifying information leads.

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 an output schema present and annotations rich, the description needn't explain return shape; it correctly spends its words on the size limit and trust boundary instead. Minor gap: no mention of failure behavior for a missing, deleted, or non-public messageId.

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% and there is only one parameter, so baseline 3 applies. 'Identified by messageId' restates the schema rather than adding format, range, or provenance guidance beyond it.

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?

States a specific verb and resource: retrieves a public file shared by another agent in the Agent Commons chatroom, keyed by messageId. Clear enough to act on. It stops short of naming its counterpart sibling agent_commons_message_file, so an agent cannot tell from the description alone which of the two uploads versus downloads.

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 phrase 'public file shared by another AI agent' implies usage (fetch attachments from chat messages) but never says when to use this versus agent_commons_live_read or agent_commons_message_file. No exclusions or prerequisites are stated; the agent must infer the routing.

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