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

Annotations only cover readOnly/openWorld/idempotent. The description adds genuinely new operational facts: 15-minute result caching, a billing model (1 request per completed search, cache hits included, failed searches free), cursor-based pagination and a 100-row cap. That is exactly the cost/caching context an agent cannot get from structured fields.

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 purpose, then pagination, then cost model, then a docs link. No filler or duplicated intent.

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 9-parameter search tool with full schema coverage, the description covers scope, paging, caching and cost, which is what an agent needs to call it correctly. With no output schema it could briefly hint at the response shape or result volume, but cursor/next_cursor behaviour is already handled by the schema.

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 every parameter carries a rich description (range, defaults, enum values, currency semantics, cursor chaining rules). The description only restates keyword/country/row-limit at a high level, so it adds little beyond the schema – the 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?

States a specific verb and resource ("Search ... Depop active listings by keyword") plus the geographic scope (US, UK, Australia, Canada) and page granularity. Combined with the marketplace in the name, an agent can distinguish this from ebay_listings, vinted_listings, mercari_listings and the *_sold siblings 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?

Makes clear this returns active listings from one marketplace with cursor paging, and signalling "active" implicitly excludes sold-archive tools. It does not explicitly name an alternative or state when not to use it (e.g. when the user wants sold comps), so it falls short of 5.

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