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

Annotations already declare readOnly, idempotent, non-destructive, so safety is covered. The description adds real behavioral context beyond that: usage counts are computed by checking references across every page, shared symbols, styles, and site settings, which explains why counts are expensive/whole-project in nature.

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, front-loaded with the scope and the reference-counting behavior, with the actionable tip last. The gallery-images-specific advice in the final sentence is slightly narrower than the tool's general scope, but nothing is wasted.

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 read-only list tool with two optional booleans, full schema coverage, and no output schema, the description is sufficient: it explains scope, count semantics, and the deletion use case. Only the shape of the returned asset/count entries is left implicit, which is acceptable given no output schema is declared.

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 coverage is 100% and both booleans are fully documented in the schema, so the baseline is 3. The description frames unusedOnly in a deletion workflow but adds no syntax or edge-case meaning beyond what the schema already states.

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 (managed assets), and scope (in the open site, with whole-project usage counts). It is clearly distinct from the other list_* siblings (pages, symbols, blocks, sites) and pairs recognizably with delete_asset.

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?

Explicitly prescribes the intended workflow: 'Use imagesOnly:true and unusedOnly:true before deleting unused gallery images.' This tells the agent when the tool is the right call and what to do with the result, though it does not name delete_asset as the follow-up sibling or state when not to use it.

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