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

Annotations already declare readOnlyHint=true and openWorldHint=true. The description adds meaningful context beyond them: the official HM Land Registry provenance, monthly update cadence, pricing model ($0.01 in USDC via x402 or prepaid credits), and free-trial availability. It does not mention pagination behavior or how 'limit' truncates results, so not a 5.

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?

Front-loaded with the resource and source, followed by returned fields and pricing. One long colon-delimited sentence carries most of the load but is dense rather than wasteful. Could be tightened but no sentence is 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-value detail is optional; the description nonetheless enumerates fields, which is redundant but harmless. Together with annotations covering safety and the description covering provenance, cadence, and pricing, an agent has what it needs. Minor gap: no coverage caveat about the England/Wales-only scope already implied by the name.

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 both postcode and limit are already documented in the schema. The description adds no parameter-level detail (e.g. what a valid postcode format is, or whether limit affects the aggregate medians), 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?

States a specific verb and resource (sold house prices for England/Wales postcodes from HM Land Registry Price Paid data), names the coverage window (1995 to date), and enumerates the returned fields. This clearly distinguishes it from geocoding siblings like uk-postcode and uk-area. An agent can identify it without opening the schema.

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 usage through the required postcode and the data-source framing, so an agent can infer it is a postcode-keyed lookup. However, it never states when to choose this over siblings such as uk-postcode or uk-area, nor any exclusions (e.g. Scotland/Northern Ireland not covered). Usage is implied rather than guided.

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