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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety and external-data status are covered. The description goes beyond them with material operational context: a metered cost of $0.05 per call, settled in USDC on Base via x402, which an agent must know before invoking a paid endpoint. It stops short of disclosing latency, rate limits, or upstream data freshness.

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?

Two compact sentences, front-loaded with the resource and its contents, followed by the scope caveat and the pricing constraint. No filler or repetition of the schema. Slightly dense in the first sentence, but every clause carries distinct information.

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?

There is no output schema, so the description correctly takes on the burden of describing what comes back: sold prices segmented by property type with change versus the previous period, EPC ratings, and crime figures. Combined with the cost disclosure and area-only boundary, an agent has enough to decide and invoke correctly; response shape and data recency remain unspecified but are secondary.

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 100%, with every parameter including defaults, ranges and the district regex documented inline, so the baseline is 3. The description adds only framing value — that district scope is a single area and that months implies a same-length prior-period comparison — and does not clarify the crime/energy toggles or the effect of months on cost or payload size.

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-and-resource combination: a UK property report for one postcode district, and enumerates the three data feeds it aggregates (Land Registry sold prices by property type with period-on-period change, EPC ratings, police.uk crime). The scope qualifier 'Area-level, no addresses' plus 'England or Wales' makes it distinguishable from the sibling epc_areas tool, which covers only the energy component.

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?

Usage is implied rather than prescribed: the agent can infer this is the right tool for aggregated area-level property research on a single district, and that full-address questions are out of scope. However, it never names an alternative or states when to prefer epc_areas (for EPC-only needs) or when a district-level rollup is insufficient, so the routing versus siblings is left to inference.

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