Biggest new-car price movers

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

Annotations already cover safety and side-effect profile (readOnly, idempotent, non-destructive), so the bar is lower. The description adds genuine value by defining 'change_percent' as change against the previous quote and by explaining how to drill into the trend, which an agent could not infer from annotations alone.

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 short sentences, front-loaded with the core operation, then the usage trigger, then the follow-up path. No redundant restatement of the tool name or schema fields.

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 change_percent and a row's name field, and 'rank' implies ordering. It omits the actual row shape and whether results are sorted descending, a minor gap for an otherwise simple, fully documented 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%, including per-parameter descriptions for days, year, limit, and direction, so the schema already carries parameter meaning. The description only loosely reinforces the freshness window through 'latest price quote' and adds no format or interaction detail beyond the schema, so the 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 and resource ('Rank new (zero-km) car variants') plus the exact ranking metric ('percent change of their latest price quote'). This cleanly separates it from sibling price tools such as kn_latest_prices and kn_price_history.

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?

Gives a concrete user-intent trigger ('which cars got more expensive lately') and routes follow-up work to kn_price_history by name. It does not state when to prefer kn_latest_prices or kn_price_list instead, so it stops short of full when/when-not coverage.

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