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

The annotations already mark the operation as read-only, idempotent, and non-destructive, so the burden on the description is lower. The description adds meaningful context: UK-registered vehicles only, official DVSA source, and the first_mot_not_due edge case explaining that expiry_date is the first MOT due date.

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 longer than minimal but each part earns its place: scope, source, returned data, special status behavior, and example queries. Some phrasing is slightly redundant, such as listing parallel user intents before the precise definition, but the structure is clear and front-loaded with the most important 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 single-parameter, read-only lookup with no output schema, the description is sufficiently complete. It lists the key returned fields, explains the special first_mot_not_due status, constrains the input to UK registrations, and gives natural-language trigger examples, leaving no essential gap for an agent to invoke it correctly.

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%, and the registration parameter description already explains case-insensitivity, spaces, GB/NI-only, and the wr25vup example. The main description repeats 'UK-registered vehicles only' and includes wr25vup in a query example, but adds no significant semantic detail beyond the 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?

The description clearly identifies the resource as the current MOT status of a UK vehicle, including expiry date, days remaining, and last test details. It avoids conflating with get_mot_history by emphasizing 'current' and 'most recent MOT test', though it does not explicitly name the sibling as an alternative.

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 provides explicit use-case examples such as 'when is my MOT due', 'has my MOT expired', and 'did it pass its last MOT', which tells an agent when to invoke it. It does not explicitly state when not to use it or which sibling should be used for full history, so it stops short of a 5.

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