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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds genuinely non-structured context: UK-only coverage, a 20-credit (20p) cost, and the critical constraint that the tool is keyed on UPRN rather than address. It does not discuss result size or failure modes for an unknown UPRN, which keeps it short of 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?

Three tight sentences: the deliverable first, then the decision rule and alternative, then the access/cost/prerequisite constraints. Every clause carries operational weight with no 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?

Coverage, cost, key type, prerequisite workflow, and the sibling boundary are all present, and an output schema exists so the return shape needn't be restated. For a single-parameter read tool this is effectively complete.

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 coverage is 0%, so the description must compensate, and it does the most important thing: it clarifies that the lone parameter is a UPRN rather than an address, and explains how to obtain one. It still doesn't state the expected format or range of a UPRN value, leaving a small gap.

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 deliverable — a one-call property summary covering identity, parent building, and headline attributes — with an explicit scope ('this property'). It also implicitly separates itself from `property_report`, which 'composes the rest', so an agent can distinguish the two without opening schemas.

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 ordering guidance ('Once you have the UPRN this is the first call to make for a specific property'), states it usually answers the question alone, and names the escalation path to `property_report`. It also supplies the prerequisite acquisition chain: `address_autocomplete` (free) then `address_resolve` to obtain the UPRN.

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