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

Beyond the readOnly/non-destructive annotations, it discloses the actual measured quantities, the shape of each check result (value, threshold, pass/fail, remediation), and two important behavioral rules: no planning value is ever invented, and without `regles` only measurements are returned. This is meaningful context the annotations cannot convey.

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?

The trigger is front-loaded in the WHEN clause, and the dense list of derived measurements and rule keys is functional rather than filler. It runs long, but each clause carries information an agent needs to call the tool correctly.

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 check tool with no output schema, the description adequately covers what is measured, what the result contains, and the critical requirement to supply externally-read rules. Scene-input parameters (murs, boites, plan) are left to the 100%-covered schema, which is acceptable given their shared conventions.

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 the baseline is 3, but the description adds real value by enumerating the meaningful keys accepted in `regles` (recul_voie_m, emprise_max_pct, hauteur_max_faitage_m, etc.), which the schema itself only shows as a vague example. This is genuine semantics beyond the schema.

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 action (measure the scene, then check against planning rules) and a specific resource (local French PLU rules), and its context ('before a building-permit application') separates it from siblings like cao_permis and cao_verifier. It stops short of naming an alternative tool outright, so it is clear but not maximally differentiating.

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?

The 'WHEN a design must be checked against the LOCAL PLANNING RULES of its zone... before a building-permit application' clause gives an explicit trigger condition, and the closing line clarifies the no-rules fallback. No explicit when-not or named alternative is given, so it is strong but not exhaustive.

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