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

Annotations already mark it read-only and open-world, and the description adds genuinely new behavior: a $0.02 per-call charge paid in USDC on Base via x402, plus the fact that a clocking warning is derived from mileage decreases and that owner data is excluded. It does not cover failure behavior for an unknown registration, but the commercial terms are a valuable disclosure.

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?

Front-loaded with the core purpose, then a dense but purposeful contents list, closing with cost and a data-scope exclusion. The enumeration is long but every item is a distinct return field, so little could be cut.

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 does the heavy lifting by enumerating returned fields, and it adds pricing and data-exclusion context. Only edge cases (invalid/unknown plate behavior, coverage period) are unaddressed.

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 both parameters are already documented, and the description's contents list maps loosely to the 'full' flag without explicitly sayings what that flag toggles. Baseline 3 applies.

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?

Names a specific verb+resource (UK MOT history for one vehicle) and enumerates the returned data precisely (make/model/age, expiry, test results, mileage, advisories/defects, repeat failures). No sibling tool covers MOT data, so the agent can route to it unambiguously.

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?

'For one vehicle' implies one lookup per registration and 'No owner data' sets expectations about scope, but there is no explicit when-to-use/when-not-to-use guidance or mention of alternatives. Usage is inferable rather than stated.

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