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

Annotations already declare read-only, idempotent, non-destructive, closed-world behavior, so the description only needs to add retrieval specifics. It does: it discloses the result set ('every seller listing'), the ordering ('in-stock whole kits first') and the returned fields (price, currency, stock, checked date, buy link, seller page), which an agent cannot get from structured fields since there is no output 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?

One sentence, front-loaded with the resource and scope, followed immediately by ordering and returned fields. Nothing is redundant and no clause could be removed without losing signal.

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 one-parameter read tool with no output schema, the description does the important work of enumerating return fields and result ordering. Minor gaps remain: it does not say whether out-of-stock listings are included alongside in-stock ones, or how many sellers are typically returned.

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 the single slug parameter is already documented as coming from search_robots, so the schema carries the load. The description adds no extra meaning such as slug format or error behavior on unknown slugs; 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?

The description gives a specific verb-equivalent ('where_to_buy') plus a precise resource: 'Every seller listing for one robot' with a known ordering. That clearly separates it from get_robot (spec detail) and search_robots (discovery), though it does not name those siblings 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 the name and the phrase 'for one robot' combined with the schema note that the slug comes from search_robots, suggesting a discover-then-purchase flow. There is no explicit when-to-use, when-not, or stated alternative, so the agent must infer the workflow.

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