ons_geo_by_uprn

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

Annotations already declare readOnlyHint and idempotentHint, so the safety profile is covered. The description adds that it returns 'all cached geographies' and explains derivation modes (ONSUD/NSUL), which is useful, but does not describe output structure, potential errors, or the meaning of 'cached' beyond that.

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?

A single sentence that front-loads the core action and includes the key mode distinction. No fluff or redundant phrasing; it is as concise as possible while conveying the primary purpose.

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?

Given there is an output schema and annotations cover safety, the description is adequate but not complete. It omits usage guidance and full parameter semantics, and does not explain the practical difference between exact and best_fit beyond the source names. For a simple lookup tool it is minimally sufficient but leaves questions.

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?

The schema has 0% description coverage, so the description must explain parameters. It explains derivationMode with its two values but does not clarify uprn (format/length), includeRaw, or the tool constant. This partial compensation is insufficient for a 0% coverage schema.

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 clearly states the tool looks up all cached geographies for a UPRN and mentions the derivation mode. It distinguishes itself from siblings by focusing on UPRN and cached geographies, though it does not explicitly name alternatives like ons_geo_by_postcode.

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?

No guidance on when to use this tool versus alternatives. It does not mention when to prefer this over ons_geo_by_postcode or other geo lookups, nor when to choose exact vs best_fit beyond the brief parenthetical. The usage context is only implied by the tool name.

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