uk_postcode_lookup

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

No annotations are provided, so the description carries the full burden. It usefully discloses the data source and that it is keyless (no API key required), but it does not mention rate limits, error behavior for invalid postcodes, or confirm read-only semantics beyond the implied 'look up'.

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?

One tightly written sentence front-loads the action and resource, then lists returned fields and the source. Every clause earns its place with no redundancy.

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 helpfully enumerates the returned data fields, which is exactly what the agent needs to know. The main gap is the lack of postcode input format, but for a simple one-parameter lookup the description is largely complete.

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%, so the single required 'postcode' parameter has no formal description. The description implies a UK postcode is passed but gives no format, spacing, or case guidance, leaving the schema description gap uncompensated.

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 gives a specific verb ('Look up') and resource ('UK postcode'), and enumerates the returned fields (town/area, region, council, country, coordinates). It does not explicitly distinguish itself from the sibling uk_postcode_nearest, so it stops short of 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?

There is no explicit when-to-use guidance or comparison to alternatives such as uk_postcode_nearest. The agent must infer that this tool is for looking up a known postcode rather than finding the nearest one.

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