Marketplace Item

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

Annotations already declare readOnly=false, idempotent=false, openWorld=true, and the description adds real context beyond them: credit consumption, the confirm=true gate, that POST reads do not publish, that creation_time may be null, and that rental listings surface listing_date_text/availability_text. It stops short of describing rate limits or failure modes, so not a 5.

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-loaded with the purpose and lookup keys, then layers return fields, rental caveats, and cost/auth notes. Dense but every sentence carries information; the middle clause about rental GraphQL fields is slightly heavy but earns its place.

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 carries the return contract itself and does so well, enumerating title, description, price, location, condition, photos, seller, availability flags, plus nullability of creation_time. Combined with the cost/auth disclosure, nothing material is missing for correct invocation.

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%, so the schema already documents all four parameters including account and confirm. The description only reinforces the id/url lookup basis and restates the confirm gate, adding no syntax or format detail beyond structured fields; baseline 3 applies.

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 (Fetches details) and resource (Marketplace item) and clarifies the two lookup keys (item id or Marketplace URL). It does not name the sibling it is distinct from (e.g. marketplace_search / marketplace_location_search), so an agent must infer the relationship rather than being routed explicitly.

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?

Usage is implied by 'by item id or Marketplace item URL' and by the confirm=true prerequisite, but there is no explicit when-to-use versus the marketplace search/location-search siblings, nor any when-not condition. Adequate but with clear gaps.

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