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

The readOnlyHint annotation already establishes it is a safe read. The description adds non-obvious behavioral context beyond that: that river/sea and surface-water risk are reported separately, and crucially that it returns an explicit absent state rather than a misleading 'low' when EA has no data. That missing-data semantics is valuable and not derivable from annotations.

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, front-loaded with what is returned and then the key caveat about absent data. No filler or repetition.

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 usefully explains the return semantics (two risks reported separately, explicit absent state). The remaining detail (exact field shapes, validation when neither parameter is supplied) is left to the schema, which is reasonable for a low-complexity lookup tool.

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%, so both postcode and property_id are already documented in the schema, including the conditional requirement and the preference for property_id. The description adds no parameter-level meaning beyond this, 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?

States a specific verb+resource (EA flood zone and surface-water risk for a property) and clarifies the two risk types are reported separately. It is clearly distinguishable from siblings like get_broadband or get_planning_history, but it does not explicitly name or contrast with any sibling tool.

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 description never states when to use this tool versus alternatives, nor any prerequisites or exclusions. Usage is only inferable from the tool name and purpose, so no real guidance is provided.

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