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

Annotations already mark the tool as read-only and idempotent, so the description does not need to repeat that. It adds useful behavioral context: the comparison uses standardized dwelling types, returns specific metrics, and applies the annexe III CGI calculation method. No contradiction with annotations.

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 description is compact and front-loaded: it states the comparison purpose, the outputs, the calculation basis, and the primary use cases in three sentences. Every sentence adds information and there is no redundant filler.

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?

Given there is no output schema, the description adequately explains what the tool returns: annual amount in euros, global voted rate, and ranking of least and most expensive communes. It also notes the standardized housing types and legal calculation basis, which is enough context for an agent to invoke the tool 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?

Schema description coverage is 100%, so the parameters are already fully documented in the schema. The description adds no parameter-level detail, but it does not need to; the baseline of 3 is appropriate when the schema carries the parameter documentation burden.

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 uses a specific verb and resource: 'Compare la taxe foncière due dans les communes d'un département' and clearly states the outputs: annual amount, global rate, and ranking of cheapest/most expensive communes. This clearly differentiates it from siblings like fiche_commune, which is about a single commune.

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?

It gives explicit use cases: 'À utiliser pour « où la taxe foncière est-elle la moins chère », ou pour situer une commune face à ses voisines.' This is clear context for when the tool is appropriate, though it does not explicitly name alternatives or state when not to use it.

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