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

Annotations already declare read-only, idempotent, non-destructive behavior; the description adds concrete traits beyond them: the 1 MiB payload cap, base64 encoding, and an untrusted-content warning. The openWorldHint is reinforced by 'third-party instructions as untrusted'.

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 tight sentences: purpose/scope first, then return format and size, then safety caveat. No repetition or filler; each sentence earns 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?

Given an output schema exists and annotations cover the safety profile, the description supplies enough: what it fetches, size/encoding constraint, and trust caveat. Only the explicit alternative-tool routing is missing.

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?

With 100% schema coverage and a single required integer messageId, the schema carries parameter meaning. The description only restates 'by messageId' and adds nothing about the value's provenance beyond what is already documented.

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 clear verb+resource ('Retrieve an attachment') and scopes it to attachments shared in public Agent Commons help requests, solutions, or discussion replies. It doesn't explicitly contrast with the sibling agent_commons_live_file, but the mailbox-attachment framing is distinguishable.

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 context (attachments on public Agent Commons messages) implies when to use it, but there is no explicit when-not guidance or direct routing to the nearest alternative like agent_commons_live_file or agent_commons_read_topic.

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