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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds useful non-annotation context: the exact data excluded (contact details, seller profiles, accounts, transaction data) and the single-page-per-location scoping constraint, which materially shapes expectations. Return format is left to the 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?

Three short, front-loaded sentences: the core action first, the data-scope exclusion second, the sibling disambiguation last. No filler and each sentence carries distinct information.

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 an output schema and read-only annotations, the description covers purpose, scope, data exclusions, and sibling routing. Minor gaps (pagination behavior across pages, result volume) are low-risk given the output schema exists, but not fully closed.

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 parameter is fully documented as 'Public Leboncoin location slug'. The description's phrase 'from one location result page' reinforces the page-level semantics but adds little syntactic or format detail beyond the schema. Baseline 3 is 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?

States a specific verb (Fetch), resource (public Leboncoin listing-card records), and scope (from one location result page), while naming the sibling tool leboncoin_listing as the alternative for single listings. An agent can distinguish this from leboncoin_listing 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_listing for one listing' names the alternative and the condition that selects it. It stops short of stating when to prefer search over broad browsing or what happens with multiple pages, but the core routing guidance is clear.

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