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

Annotations already cover read-only/idempotent/no-destroy behavior, and the description adds real value beyond them: the URL is short-lived (a freshness constraint), access is 'authorized', and downloaded content is explicitly untrusted with the caveat that a 'ready capture is not proof that its bytes were read'. That is meaningful context an agent would otherwise lack.

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?

Two sentences, purpose front-loaded, no filler. The second sentence is terse and slightly cryptic ('ready capture... bytes were read') but is short enough that it does not bloat the definition.

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, the description needn't explain return values, and it covers purpose plus the security/freshness caveats. The remaining gap is workflow placement relative to attachment discovery, which is a minor omission for a simple read tool.

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 all four parameters (including the optional asset_id and its null fallback) are already documented. The description adds no parameter-level detail beyond what the schema provides, which is the expected baseline when schema does the work.

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 states a specific verb ('Fetches') and resource ('attachment projection and short-lived download URL'), making the operation distinguishable from siblings like inbox_messages or inbox_read. It does not explicitly name which sibling to use instead, keeping it a step below full differentiation.

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?

There is no guidance on when to call this tool versus inbox_messages, inbox_read, or inbox_message_reconcile. The only relational hint ('asset_id from inbox_messages') lives in the schema, not the description, leaving the agent to infer the workflow.

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