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

Annotations already state readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds auth requirements (Bearer chu_live_…), result-count limits per tier (10 vs 25), the deal-score gating by tier, and the presence of source_url in each listing with a citation instruction — all behavior beyond the 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?

It is front-loaded with the core purpose, then the aggregation sources, then access tiers, then the source_url citation rule — a logical ordering. The bilingual EN/FR duplication adds some length without new meaning, keeping it just below top marks.

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 partially compensates by noting that listings carry source_url and deal-score. It covers auth, limits, and aggregation scope, so an agent has enough to call it correctly; only the sibling-routing detail is absent.

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 93%, so parameters such as model, region, and sort are already well documented in the schema. The description adds tier context around limit and deal_score, but does not add syntax or format meaning beyond what the schema already provides, making the baseline 3 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?

The description names a specific verb and resource ('Search used cars for sale in France'), names the aggregation sources (CarHunt over LeBonCoin, LaCentrale, L'Argus…), and scopes the free vs. keyed tiers. An agent immediately knows this is a multi-criteria aggregated search, distinguishable from single-valuation siblings like estimate_car_price.

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?

It clearly conditions behavior: without a key, 10 results and no deal-score; with a Premium/Pro/Expert key, 25 results plus deal-score and deal_score sorting. That is concrete when-to-use guidance tied to access level. It stops short of explicitly routing between this and sibling tools such as pro_search or pro_deals.

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