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

Annotations already declare readOnly/idempotent/non-destructive, yet the description adds substantive methodology: only published daily rates are used, a price change requires two plausible rates within 30 days with the new one still live, new arrivals exclude re-scraped re-listings and bulk imports, and unknown places return did_you_mean. These are non-obvious inclusion rules an agent cannot infer 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?

Purpose and the enumerated lenses are front-loaded, and the edge-case rules follow in a logical order. It is dense but mostly earns its length; the main waste is re-stating enum meanings (rarest, new_arrivals, price changes) that the schema already documents in full, which makes it longer than necessary.

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 read-only, four-parameter tool with an output schema, this covers what an agent needs: what each kind yields, geographic scoping, and the did_you_mean fallback for unknown places. Return values are handled by the output schema, so nothing material is missing.

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 baseline is 3. The description still adds the scoping model — "nationwide or in a state or city" — clarifying how state/city interact with the result set, which the bare schema does not. It does not, however, specify behavior when both city and state are supplied, so it is not a full 5.

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?

Opens with a specific verb+resource ("Show what is interesting in the exotic rental catalog") and enumerates the seven distinct lenses (new listings, price changes, rarest families, most expensive, biggest fleets, most reviewed). An agent can distinguish this highlights/roundup tool from search_vehicles or top_companies without opening any 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?

Gives concrete trigger questions ("what's new", "what got cheaper", "what's the rarest car I can rent", "who has the biggest fleet in Miami") and frames itself for news-style summaries, which tells the agent when this tool fits. It does not name a sibling alternative or state when NOT to use it (e.g., for targeted vehicle search), so it stops short of the 5 bar.

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