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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds genuinely useful behavior beyond that: the ONS data source, the exact breakdowns returned, and a concrete cost model ($0.01 per call, paid in USDC on Base via x402), which is critical for an agent deciding whether to invoke a paid tool.

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?

One dense sentence that front-loads the metric and scope, then the breakdowns, then the price. Every clause carries information, though the pricing clause could be split for readability and the sentence is long enough to be slightly harder to scan than ideal.

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 no output schema, the description carries the burden of describing returns, and it does: overall rent, by bedrooms (1 to 4+), by property type, and yearly change. Combined with the documented input and the disclosed per-call cost, an agent has everything needed to call this correctly.

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% and the single 'area' parameter is already documented with examples (Manchester, M20). The description restates the accepted forms (council name or the council of a postcode district) but adds no new syntax, normalization, or ambiguity-resolution detail beyond the schema, so the baseline 3 applies.

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 names a specific resource and metric: average monthly private rent (ONS) for a UK council or postcode district, with breakdowns by bedrooms and property type plus yearly change. That is far more specific than the title 'property rents' and clearly separates it from area/flood/EPC siblings by data content, though it never names an alternative tool 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?

Usage is only implied: an agent can infer it should call this when it needs rent levels for a named council or postcode district. There is no explicit when-to-use/when-not guidance and no pointer to property_compare or property_area for related questions, so routing must be inferred from the resource description alone.

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