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

Annotations already declare read-only, idempotent, non-destructive and closed-world, so the safety profile is covered. The description still adds real value: it states the call is free and keyless, that nothing is executed or charged, and that the success_rate is read from the listing record over a 7-day window (i.e. it is cached/stored, not freshly measured) — a meaningful caveat an agent would otherwise miss.

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 with the resource and payload front-loaded, followed by the return detail and the cost/side-effect note. Only the clause 'read from the listing record, so check it before buying' is slightly padded, blending return-value detail with guidance.

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 no output schema, the description usefully names the return shape (manifest, schemas, pricing_summary.price_per_1k_usd, success_rate with window) and the zero-cost/zero-execution guarantee. Only the omitted-version default behavior is left unexplained for a 2-parameter 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 both slug and version are already documented, and the description's slug reference merely echoes 'from alterlab_store_search'. It adds no semantics for the optional version pin (e.g. what happens when it is omitted). Baseline 3 is appropriate.

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 opens with a concrete verb and resource ('Get one listing') and enumerates the payload: manifest with input/output schema, price per result, live reliability. It is clearly distinct from alterlab_store_search (which supplies the slug) and from alterlab_store_run/alterlab_store_quote. It stops short of an explicit 'not for searching' statement, so a 4 rather than 5.

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?

'check it before buying' and 'nothing is run or charged' give an implicit when-to-use (pre-purchase inspection) and when-not-to-expect-work (no execution). The slug's provenance is pointed at alterlab_store_search. No explicit exclusion naming store_run or store_quote as the execution step, so it is context rather than full routing guidance.

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