postcode_random

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

Annotations already declare readOnly, non-destructive and open-world, so the safety profile is covered. The description additionally promises 'full location details', which is useful given there is no output schema, but it does not say what those details include or that repeated calls return different results — a point worth flagging since idempotentHint=true is questionable for a random generator.

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?

A single front-loaded sentence with no filler. The distinguishing attribute ('random') and the scope ('UK') both appear before any payoff clause.

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 no-parameter, no-output-schema utility this covers the essentials: what it returns at a high level and that it is randomised. It would be stronger if it enumerated the location fields or noted that the result varies per call, but nothing critical to correct invocation is missing.

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?

The tool takes zero parameters, so there is nothing for the description to explain; baseline 4 applies. The absence of any options is consistent with the empty schema.

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 ('Get a random UK postcode') plus a hint at the payload ('full location details'), which is enough to distinguish it from the deterministic sibling postcode_lookup. It stops short of naming that sibling explicitly, so the differentiation is implicit rather than stated.

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 gives no when-to-use guidance and no mention of the obvious alternative (postcode_lookup for a known postcode) even though that sibling sits right next to it. An agent has to infer the choice from the word 'random' alone.

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