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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the safety profile is covered. The description adds valuable behavioral context: distance is measured to centroids, results are ordered nearest-first, and the nearest commune may not contain the point. This goes beyond the annotations and helps the agent interpret results correctly.

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?

Two sentences with no wasted words. The core behavior is front-loaded, and the caveat plus sibling alternative is packed into the second sentence. Every clause earns its place.

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?

The tool has an output schema, so return values are documented elsewhere. The description covers the key behavioral nuance (centroid distance) and the sibling distinction. A small gap is that it doesn't mention the default radius/limit, but those are already in the input schema, so the description is complete enough for an agent 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?

Schema description coverage is 100%, so the schema already documents all four parameters (lat, lng, limit, radius_km) with types, bounds, and defaults. The description adds the centroid-distance semantics but doesn't need to repeat parameter details. Baseline 3 is appropriate because 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 states a specific verb ('Communes within a radius of a point') and resource, and explicitly distinguishes itself from the sibling commune_at by explaining the centroid-distance behavior. This makes the tool's purpose unmistakable and differentiates it from the sibling that returns the commune containing the point.

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 description explicitly says when to use this tool versus commune_at: use this for communes within a radius, and commune_at for the commune that contains the point. It also clarifies the nearest-first ordering and the centroid caveat, which is essential for correct selection.

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