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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds genuinely new behavioral context beyond the annotations: a metered access model ('a few free samples a day, then $0.005 USDC per call via x402'), which is important operational information an agent cannot get from structured fields.

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, front-loaded with the analytical content the agent needs and followed by the access/cost note. Every clause carries information; nothing is redundant.

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 an output schema present and full schema coverage, the description need not explain return structure, and it correctly focuses on scope plus cost. The only shortfall is the absence of any cue about how this summary relates to sibling property endpoints, which would complete the selection picture.

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%, with both 'postcode' and 'years' documented (years with its default of 5). The description mentions 'in a postcode over N years', reinforcing the semantics but adding no syntax or format detail beyond the schema, so the baseline 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?

The description names a specific resource (sales in a postcode over N years) and enumerates the exact statistics returned (count, median, mean, range, by-type medians), which is more precise than a vague verb. It does not, however, distinguish itself from close siblings such as uk-property__sold-prices or uk-property__house-price-index, leaving the agent to infer the boundary.

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 statement of when to use this tool versus the many adjacent property data tools. The only usage-adjacent text is the pricing model, which tells the agent about cost but not about selection between alternatives, so an agent cannot confidently route between this and sold-prices.

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