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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so safety is covered. The description usefully adds the pricing/allowance model, which no annotation provides and which an agent must know before calling. It stops short of covering result volume or the effect of a large dist.

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 sentences, front-loaded with the resource and location scope before the pricing caveat. No filler.

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-value explanation is not required, and the description names the station categories returned plus the cost model. What is missing is any hint about the maximum usable radius or expected result counts for an open-world spatial query.

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 description coverage is 100% (lat, long, dist all documented with the km default), so the schema carries parameter meaning. The description adds nothing about coordinate format or a maximum radius, so 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?

States the resource (river level, flow, tidal and rainfall monitoring stations) and the spatial scope ('near a point'), which separates it from uk-flood__river-stations and uk-flood__rainfall-near. It does not explicitly name those siblings, so a reader must infer the distinction from the resource wording alone.

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?

The only guidance is commercial: free within the daily allowance, then $0.002 USDC per call via x402. There is no statement of when to prefer this over uk-flood__rainfall-near, uk-flood__tide-gauges or uk-flood__river-stations, nor any note on radius or result-count limits.

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