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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds genuinely new behavioral facts: 'UK only' geographic scope, a 20-credit cost, and that the call is keyed on UPRN rather than address. No auth or rate-limit context, but the cost and coverage disclosures are the high-value items.

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 purpose, then routing, then constraints — a sensible ordering. Every sentence carries information, though the address-resolution detour is slightly tangential to a summary call and could be trimmed.

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 the description need not describe return fields, and it otherwise covers cost, geography, input identity, and the relationship to `property_report` and the address-resolution chain. Nothing an agent needs in order to call this correctly is missing.

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% for the single `uprn` parameter, so the description must compensate — and it does, clarifying that the key is a UPRN and not a postal address, plus how to obtain one via the address_* siblings. It does not state the expected format or range of the integer, which keeps it short of a 5.

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 ('One-call summary of a property') and enumerates what it covers: identity, parent building, and headline attributes. It explicitly differentiates itself from the sibling `property_report`, which 'composes the rest', so the agent can distinguish the two without reading either 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?

Gives explicit sequencing: once the UPRN is known, 'this is the first call to make for a specific property', and points to `address_autocomplete` (free) then `address_resolve` when the UPRN is unknown. It also names the alternative (`property_report`) and the condition under which it is needed.

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