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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so safety is covered. The description meaningfully adds what the annotations do not: a metered pricing model (a few free samples per day, then $0.002 USDC per call via x402) and a bounded result set ('50 most recent'), both of which affect how an agent should budget and call it.

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, front-loaded with the subject matter and time span before the commercial terms; nothing is redundant. The pricing clause is useful but slightly tangential to the tool's function, keeping it just short of a 5.

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?

For a one-parameter, read-only tool with an output schema and safety annotations already covering the return contract, the description is close to sufficient. It discloses cost and result limits, but omits error behavior for invalid LSOA codes and any routing hint against its three siblings.

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 coverage is 100% for the single `code` parameter, so the baseline is 3, but the description goes beyond the schema by explaining what the parameter denotes — a 2021 LSOA, a neighbourhood of roughly 1,500 people — which tells the agent what geographic granularity it is requesting. It still does not describe the code's format or give an example.

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: collisions within a 2021 LSOA, with the temporal window (five years) and the result cap (50 most recent). The scope ('neighbourhood of ~1,500 people') implicitly distinguishes it from the local-authority sibling, but no sibling is named, so the differentiation is left to inference.

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?

There is no explicit when-to-use or when-not-to-use guidance and no reference to the alternatives (uk-road-safety__collision, __near, __local-authority). The pricing sentence describes cost, not the conditions under which this tool should be chosen over a broader collision query.

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