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

With readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false already present, the safety profile is covered. The description adds useful behavioral context beyond those annotations: it is restricted to UK-registered vehicles, it draws on DVSA/DVLA/HPI data, and it explains that MOT and tax status are part of the result. It does not describe error handling for invalid registrations, but that is a minor gap.

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?

The description is front-loaded with the hard constraint 'UK-registered vehicles only,' then gives the purpose, then the invocation context. The example query list is long but earns its place because it helps an agent recognize varied phrasings for the same lookup.

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?

The tool is simple (one required parameter), the schema already documents the registration format, annotations cover the safety/state behavior, and the description enumerates all visible return fields. Nothing an agent needs to decide to call it or interpret its result 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?

Schema description coverage is 100%, so the baseline of 3 applies. The tool-level description reinforces the meaning by showing example registrations in natural-language queries, but it adds no format, normalization, or edge-case guidance beyond what the schema already provides.

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 specific verb ('look up') and resource ('UK number plate') and enumerates the exact returned attributes: make, model, colour, year, fuel type, age, MOT status/expiry, and tax status/due date. The final sentence's 'best first call for any general question' positions it as the general-purpose sibling to the dedicated MOT tools, so it distinguishes itself from get_mot_history and get_mot_status.

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 explicitly frames this as 'the best first call for any general question' and provides seven concrete example queries, which tells an agent when to reach for it. However, it never names the sibling tools or says when to prefer get_mot_status/get_mot_history, so exclusions and alternatives are left implicit.

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