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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds non-redundant behavior: a geographic restriction (UK only) and a concrete per-call price of 30 credits, both of which materially affect whether and how an agent calls it. It stops short of describing result volume or how the limit parameter bounds output.

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 short sentences, each doing distinct work: definition, differentiation, then constraints. The identifying criteria and the UK-only/cost caveats are front-loaded 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?

An output schema exists and annotations are rich, so return values and safety need no explanation. What is missing is the practical calling detail for a 0%-documented schema: no hint about what an area_id looks like (a relevant sibling, area_resolve, exists) or how limit and the two minimum thresholds interact.

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% across four parameters, so the description must carry the load and largely doesn't. The 'BOTH residential and commercial' framing loosely implies that min_residential and min_commercial are thresholds of at least 1, but area_id, limit, and their formats/defaults are never addressed.

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 concrete resource and the defining filter: buildings holding BOTH residential and commercial units, framed as the 'conversion and permitted-development cohort'. The line 'a property of the building's unit mix, not an attribute of any single property' implicitly separates it from property-level siblings like property_lookup or commercial_property, though no sibling is named outright.

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?

It supplies real usage constraints — 'UK only' and a 30-credit (30p) cost — which an agent needs before calling. However, there is no guidance on when to prefer this over adjacent tools such as commercial_property, property_summary, or area_stock_profile; the agent must infer the boundary from the unit-mix framing.

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