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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, non-destructive, closed-world), so the bar is lower. The description adds real behavioral context beyond that: trailing-window semantics, UK-only geography, and the fact that it is free. It does not disclose ordering/pagination behavior, but it clears the bar the annotations set.

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: purpose and examples front-loaded, scoping rule next, and scope/cost constraints last. Every clause earns its place and nothing is redundant.

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, so return values needn't be described. The description covers the key scoping inputs and geographic limits, but given 5 undocumented params it would benefit from noting the default window and the richer order_by options.

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?

With 0% schema description coverage, the description carries the full burden. It meaningfully explains `county` and `area` (with worked examples and the omit-both default) and implies `months` via 'trailing window', but leaves `limit` and the 9-option `order_by` enum largely unexplained — only 'volume or median price' is implied, not p25/p75 or new-build variants.

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 (Rank) and resource (postcode districts) with the ranking dimension (transaction volume or median price). It implicitly separates itself from siblings like market_volume_series (a series) and market_ranking, though it never names an alternative to differentiate explicitly.

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?

Provides concrete triggering examples ('busiest districts in Greater London last year', 'priciest districts in SW') and states the selection rule for scoping — use county or area, or omit both to rank nationally. It stops short of naming sibling alternatives or stating when NOT to use it.

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