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

Goes well beyond the readOnlyHint/openWorldHint annotations by disclosing the retrieval mechanism (stealth proxy), the billing model ($0.03 USDC per successful call via x402 on Base/Solana/Arc), and that failed calls are free — decision-relevant context an agent cannot get from structured fields. It does not say anything about rate limits or result freshness, keeping it short of a 5.

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 scope come first, followed by cost/mechanism, with no filler sentences. The long enumeration of returned fields is somewhat redundant given an output schema exists, which is the only thing keeping it below a 5.

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 two-parameter read-only scraper with an output schema and annotations, the description covers source, scope, cost, and failure billing — everything needed to call it responsibly. Missing only freshness/staleness and rate-limit expectations.

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%, so both `query` and `page` are already documented in the schema. The description adds one useful detail — 35 ads per page — which clarifies the granularity of `page`, but nothing about query syntax or paging limits beyond what the schema says. Baseline 3.

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 (leboncoin.fr classified-ads search) with an explicit geographic scope (all of France) and enumerates what the results contain. No sibling tool in the list does classified-ad search, so the agent can place it immediately.

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?

Usage is implied by the query example and the 'all of France' scope, but there is no explicit statement of when to reach for this tool versus alternatives, nor any exclusion or prerequisite beyond payment. With no close siblings the cost of that gap is low, but the guidance is inferred rather than stated.

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