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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, yet the description adds substantial behavior the annotations cannot carry: no individual listings are ever returned, the data has a calculation date and is not served beyond 45 days, and a collection-update month returns only new listings plus displayed price (and says so). It also discloses aggregation provenance (Pillr-collected sale listings, end-of-month).

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 purpose is front-loaded in the opening clause, which is good. But the remainder is a single sprawling sentence larded with nested parentheses and semicolon clauses, making it hard to parse and scan. Information density is high with little pure filler, yet structure and readability suffer.

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 carries the full burden of explaining return content — and it does so exhaustively: every metric returned, the source and aggregation method, the calculation date, the staleness cutoff, the partial-month caveat, and what is explicitly excluded. An agent needs nothing further to call it correctly.

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?

There is a single parameter with 100% schema description coverage, and that schema text is already very rich (commune name, code INSEE, arrondissement formats, postal-code fallback). The description body adds no parameter-level detail beyond the schema, so the baseline of 3 applies.

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 the resource precisely and enumerates the concrete payload (prix au m² appartement/maison, loyer médian DHUP, loyer par type T1→maison avec fourchette 95%, rendement brut, évolution 1/3 ans, zone ABC, marché vente du dernier mois). An agent knows exactly what comes back. It does not, however, name or differentiate itself from the sibling prix_m2_commune, which is the closest alternative, so it stops short of a 5.

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 only implied: it is framed as an 'aperçu' and explicitly states that the Pillr score, sub-scores and full analysis are not served here but live on pillr.fr. That is a scope boundary rather than a routing rule. There is no explicit when-to-use-this-vs-prix_m2_commune guidance, though the 45-day staleness note is a usable operational constraint.

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