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

Annotations cover the read-only/idempotent safety profile, and the description adds substantial context beyond them: cost (5 credits), geographies (UK only), keying (UPRN rather than address), and three separate interpretation traps — asking vs achieved rent, p25–p75 for area_asking, gross vs net yield, and LHA being a benefit cap rather than a market rent.

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 deliverable before the caveats, and every paragraph maps to a distinct output block. The prose is dense but the length is justified by the misinterpretation risks it defuses; a few sentences run long.

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 structure needn't be explained, yet the description still supplies the interpretation semantics for each returned block (basis, gross yield, LHA, shared-room rate). Nothing needed to call or correctly read the tool is missing for this complexity level.

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 carries the burden. It compensates well for uprn (integer UPRN, obtain via address_resolve), but the optional beds parameter is never named or explained — only 'bedroom band' appears, in the context of area_asking, which does not clearly tell the agent what beds does.

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?

Opening sentence states a specific deliverable — what the property would let for, plus its basis — which cleanly separates it from siblings like lha_rate, market_yields and valuation_estimate. It also pre-empts the most likely confusion by naming the three basis variants and explicitly noting that unit_hedonic does not exist.

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?

Gives an explicit prerequisite workflow (address_autocomplete is free, then address_resolve to obtain the UPRN) and constrains scope to UK only. It does not, however, state when an agent should reach for this tool instead of valuation_estimate or market_yields, so a routing gap remains.

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