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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so safety is covered. The description adds genuinely new behavior: links expire after roughly two hours, no re-render work is performed, and an optional hash verification exists. It stops short of describing the returned payload or any expiry of the refreshed links themselves.

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?

A single front-loaded sentence with the trigger condition first, then the input source, then the freshness constraint. No filler or repetition of annotation-derived facts.

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 two-parameter, non-destructive read with no output schema, the description covers trigger, input provenance, and link lifetime. The only gap is what the response contains (link objects vs. bare URLs), which the phrase "fresh links" only implies.

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 50% schema coverage, the description carries real weight: it tells the agent where ids come from (an earlier sfx or render result) and that verify is a hash re-check. The minItems/maxItems bounds (1–16) are only in the schema, but the description covers the semantics the schema leaves thin.

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 action and resource: renewing download links from previously returned asset ids, explicitly with "no re-render." It also names the sibling tools whose results supply the ids ("from an earlier sfx or render result"), so an agent can separate this from render/sfx without opening a 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?

"Use this when a download link was lost or is about to expire" gives an explicit trigger condition, and "no re-render" steers the agent away from re-running render as the alternative. There is no explicit statement of when not to use it (e.g., ids from other sources), but the routing context is clear.

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