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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld). The description adds real value beyond them by disclosing the cost model: free within a daily allowance, then $0.001 USDC per call via x402. It does not mention authentication or rate-limit specifics, but for a read-only lookup the cost disclosure is the meaningful additional trait.

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 short sentences with the returned fields front-loaded and the pricing note second. The first sentence is a fragment lacking an explicit verb, but no words are wasted.

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 the description need not explain return values, and annotations carry the safety profile. It still omits how to source a valid ward code and any routing to the sibling that resolves codes, which an agent would need to use this tool end-to-end. Adequate but with a clear gap.

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% and there is a single required parameter ('code', documented as an ONS ward code), so the schema does the heavy lifting. The description adds nothing about the identifier format or where to obtain it, making the baseline 3 appropriate.

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 names the resource (a ward) and enumerates exactly what is returned: local authority, county/unitary, region, country and Westminster constituency. That makes the tool's job clear even without a verb. It does not explicitly differentiate itself from siblings like uk-geography__local-authority or uk-geography__county, which are the same shape applied to other geography levels.

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 guidance on when to use this tool versus alternatives, nor on prerequisites such as needing a valid ONS ward code (which would come from uk-geography__search). The only directional information is commercial (pricing), not usage-oriented.

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