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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so the safety profile is covered. The description still adds genuine behavioral context beyond them: 'Free and public', the exact returned fields, and the important limitation that no polygon is included.

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?

Three tightly packed sentences: what it finds, how to narrow it, what comes back and what to do next. No filler, and the core purpose is front-loaded before the filter and return details.

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 compensates by enumerating the returned fields (id, kind, admin_level, country, parents, bbox, centroid, population) and flagging the absent polygon. Combined with the onward pointer to get_boundary, an agent has everything needed to call this 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 all six parameters are already documented, including the enum and the lat,lon pattern. The description restates which filters exist ('country, kind or admin_level', 'bias toward a point with near') but adds no syntax or semantics 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?

States a specific verb and resource — 'Finds administrative boundaries ... and postcode areas by name, in any language' — and enumerates the covered kinds. An agent can distinguish this from reverse_boundaries or get_boundary from the description alone.

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?

Explicitly routes the agent onward: results carry no polygon, 'pass the id to get_boundary for that', which is a real when-to-use-next rule. It does not, however, distinguish this from siblings like reverse_boundaries (coords → boundary) or contains_points, so the exclusion coverage is partial.

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