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

Annotations already declare readOnly, idempotent, non-destructive and openWorldHint=false, so safety is covered. The description adds genuinely new context: the data source (Environment Agency surface-water, i.e. not river/sea flooding), the geographic restriction, that it is free to call, and that it fails without a UPRN — behavioral facts not present in the 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?

Three compact lines with the identity, scope/constraint, and the prerequisite workflow front-loaded. No filler, no restatement of the title, and the most load-bearing constraint (UPRN, not address) comes last where it acts as a call-to-action.

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?

For a one-parameter read tool with a full output schema, the description covers everything the agent needs: what the tool returns conceptually, its cost, its geographic limits, and how to satisfy the required argument. Return-value details are correctly left to the output schema.

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 0% for the single parameter, so the description must compensate, and it does: it explains that the key is a UPRN (not a free-text address) and how to obtain one via the address tools. It does not state the expected UPRN format/validity range, which the schema's bare 'integer' type leaves unaddressed.

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?

Names a specific verb+resource ('surface-water flood risk for a property'), pins the authoritative source (Environment Agency), and constrains scope ('UK only'). An agent can distinguish this from the broad property_risk_report siblings because the data domain and keying are stated outright.

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?

Gives explicit operational guidance: UK only, free to call, and requires a UPRN rather than an address, with the prerequisite chain (address_autocomplete -> address_resolve) spelled out. It stops short of saying when to prefer this over sibling risk tools such as property_risk_report, which likely bundles flood risk with other perils.

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