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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower, and the description still adds substantial context: credit cost, null-rather-than-estimated semantics for year_built/num_floors, which height field to use, attribution preservation, and explicit limits of what the extrusion shows. That is behavior well beyond the annotations.

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 what is returned, then caveats, then the boundary/cost/input-key rules. Every sentence carries a distinct, actionable constraint; nothing is restated from the schema or annotations.

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?

For a single-param, read-only lookup the description covers inputs, cost, coverage, null handling, field-selection pitfalls, and rendering caveats. An output schema exists, yet the field enumeration still usefully frames the response; nothing an agent needs to call it 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% and there is 1 required param, so the description must carry the meaning — and it does, clarifying that the key is a UPRN (integer identifiers for buildings) and not an address, plus how to obtain valid values. It stops short of stating format/plurality expectations for the array itself.

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 resource (physical form of buildings a set of UPRNs sit in) and enumerates the exact attributes returned (height, volume, footprint, floors, materials, basement, green roof, solar, unit mix). An agent can distinguish this from near-neighbours like property_summary or address_by_uprn without opening a 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?

Explicitly says it is UK-only, costs 15 credits, and is keyed on a UPRN not an address, then names the exact pipeline: address_autocomplete (marked free) to narrow, then address_resolve to obtain the UPRN. This is when-to-use, prerequisite, and alternative in one passage.

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