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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description's only incremental disclosure is pricing ('Free'), which is genuinely useful but thin; no rate limits, result caps, or pagination behaviour are mentioned.

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 short sentences, both front-loaded and information-bearing, with zero filler. Nothing could be cut without losing meaning.

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 single-parameter lookup with an output schema present, the description need not explain return shape. It is adequate, though it omits postcode formatting expectations and any result-volume caveats that would matter for a bulk address lookup.

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 0% and the single parameter has no description, so the burden falls on the prose. The description adds only the qualifier 'UK postcode', which is useful format context but nothing about normalisation, spacing, or partial-postcode behaviour.

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 and resource ('Return all addresses at a UK postcode'), so the operation is unambiguous. It does not, however, differentiate itself from close siblings like address_by_uprn, address_autocomplete, or address_resolve, so an agent must infer the boundary.

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?

Beyond the cost signal 'Free', there is no when-to-use guidance, no mention of when to prefer address_by_uprn or address_resolve, and no prerequisite (e.g. postcode format or coverage limits). The agent gets no routing help.

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