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

The annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, so the safety profile is covered. The description adds genuinely new behavioral information: this is a metered call charged to a Stratum API balance, with a test-key alternative — a cost/auth trait no structured field conveys. It stops short of describing the response shape or what happens when a postcode has no records.

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, no filler, and the highest-value information (what data domains are returned) is front-loaded. The billing caveat is correctly placed second as a secondary constraint.

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-only lookup this is nearly complete: the agent knows the scope, the domains covered, and the cost model. The remaining gap is return-value description — there is no output schema, so the agent must guess the structure and size of the multi-domain payload it is paying for.

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?

There is a single parameter with 100% schema description coverage ('UK postcode, for example TA7 0RB'), so the schema already carries the semantics. The description adds nothing about format normalization, case, or partial-postcode handling beyond what the schema states, 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 concrete resource (a UK postcode report) and enumerates exactly what the report covers: flood risk, crime, deprivation, coal mining, radon, contaminated land and Japanese knotweed. That makes it trivially distinguishable from every sibling (company_*, fca_*, sanctions_*, epc_for_address), though it never explicitly states the differentiation, which keeps it just below a 5.

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 this is the tool for property/area due diligence on a UK postcode. No when-to-use, when-not-to-use, or alternative is stated — it never tells the agent whether to prefer epc_for_address, run_suite_check, or another sibling when scopes overlap. The only explicit operational guidance is the billing note.

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