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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), but the description adds a substantial data-interpretation caveat not present in any structured field: n_guide and n_achieved are computed over different populations, so differencing them is meaningless. It also explains the `comparable` output flag and prescribes fallback reporting behavior when it is false.

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 one-line purpose, then usage routing, then the critical caveat. Sentences are dense but each carries non-obvious information; the warning block is long relative to the rest, though it is genuinely high-stakes context rather than padding.

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, return values need not be re-explained, and the description still adds the key output-semantics note about `comparable`. Scope, time formatting, and geographic limits are covered; the remaining gap is the unexplained is_commercial and limit parameters.

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% across 5 params, so the description must carry the load. It documents quarter_from/quarter_to format precisely (first day of a quarter, e.g. 2024-01-01) and the geographic scope, but says nothing about is_commercial, limit (default 50), or postcode_district format — three params left entirely to the schema's bare types.

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+granularity: "Quarterly UK auction statistics by postcode district", and enumerates the metrics returned (lots offered, lots sold, sale rate, average guide/achieved/net yield). It explicitly distinguishes itself from auction_lots as the individual-comparables sibling.

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 an explicit positive condition ("the shape of a local auction market over time — is it clearing, are yields moving, is stock rising") and names the alternative tool with the condition that selects it ("For individual comparables use auction_lots"). Also states constraints: UK only, free.

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