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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds genuinely new behavioral context absent from annotations: the pricing model (free within daily allowance, then $0.001 USDC per call via x402), which materially affects an agent's call strategy.

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 tight sentences: the returned payload is front-loaded, then the cost note. No filler or redundancy, though it could be marginally tighter.

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, the return shape need not be described; the rich annotations carry the safety profile; and pricing is disclosed. Everything an agent needs to call this correctly is available.

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 'id' parameter is documented in the schema as 'Bathing water id'. The description adds nothing about id format or sourcing, so the baseline of 3 is appropriate when the schema does the work.

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 resource ('One bathing water') and enumerates what it yields (classification+year, pollution-risk forecast, sample date, water company, profile link), so the agent knows exactly what 'site' means. It implies the by-id lookup distinction from siblings bathing-water__near/search but never names them, so it falls short of full sibling differentiation.

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: the 'by id' framing and the single required id parameter make the lookup nature obvious. There is no explicit when-to-use guidance and no pointer to bathing-water__search for discovering an id, which would have been the natural routing instruction.

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