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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, but the description adds operationally important context: references are private to the API key, at most 10 are live at once, each expires 7 days after last use or re-upload, and the call costs no credits. These constraints are not derivable from the annotations or schema.

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-loads what is listed and its ordering, then the use case, then the operating constraints. Dense but every clause carries new information; no filler or repetition of the tool name.

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 parameterless read tool with an output schema, the description covers everything the agent needs: purpose, ordering, per-item contents, the recovery use case, privacy scoping, the 10-item cap, the 7-day expiry rule, and the zero credit cost.

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?

The tool takes zero parameters, so the baseline is 4 per the rubric. The description goes slightly beyond by naming the fields in each returned record (ref_ token, upload URL, expiry, image-in-place flag, source generation image), which helps even though an output schema exists.

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 (list), resource (live reference images), scope (live, private to API key), and ordering (most recently used or uploaded first), then enumerates the fields returned for each item. The 'recover a token you lost instead of uploading the image again' clause implicitly contrasts it with create_reference, so the agent can distinguish it from siblings.

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?

Gives a clear scenario ('Use it to recover a token you lost') and names the alternative it replaces ('instead of uploading the image again'), which points at create_reference. It does not state any when-not conditions or other valid uses (e.g. auditing expiry), so it falls short of fully explicit routing.

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