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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world). The description adds genuinely non-structured context: geographic coverage is UK only, the call is free, and it explains why type_id is required (one area per geography layer, otherwise ambiguous). That is meaningful beyond the 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?

Three short sentences, front-loaded with the core operation, then the required-parameter rationale, then scope/cost. No 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?

An output schema exists, so return values need no explanation, and annotations cover the safety profile. The description covers scope, cost, and the key required param; the only minor gap is that it doesn't hint where an agent obtains a valid type_id.

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 0%, so the description must carry the load. It thoroughly explains the non-obvious parameter, type_id (an area type UUID, required, and why), which is the one that would otherwise confuse an agent; lat/lng are conventional and need no elaboration.

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+resource: it returns the area of a given type that contains a coordinate, which is a distinct operation from siblings like area_resolve or area_report. It is clear what the tool does, though it does not explicitly contrast itself against any named sibling.

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 implies the use case (you have a lat/lng and want the containing area) and adds scope constraints (UK only, free), but it names no alternative tool and gives no explicit when-to-use/when-not guidance versus area_resolve or parcel_lookup.

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