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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds that only public ads are fetched and that the URL must be caller-supplied, but says nothing about rate limits, invalid/non-canonical URL behavior, or error handling. Adequate but not rich.

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?

Two sentences, zero waste, with the core action front-loaded and the routing hint immediately after.

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-param read tool with annotations covering safety and an output schema covering return values, the description is essentially sufficient. Only minor gaps remain, such as what happens when the supplied URL is not a valid listing.

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% and the single url parameter is fully documented as a canonical public ad URL from leboncoin-search. The description's 'caller-supplied' phrasing reinforces but does not add syntax or format detail, so the schema does the heavy lifting.

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 ('Fetch one ... Leboncoin listing') and scopes it ('caller-supplied public'), which distinguishes it from the sibling leboncoin_search without opening either 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?

Explicitly routes the agent: use leboncoin_search to find listings or discover a listing URL before retrieving. The alternative and the pre-condition are named, though it does not spell out failure cases (e.g. a search-page URL being passed in).

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