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

Annotations already establish read-only, idempotent, non-destructive, closed-world behavior, so the description is not obligated to restate safety. It adds genuinely new context: the check pulls live MOT and tax from DVLA, insurance has no public API (askMID manual declaration), and the response is a pass/fail decision with recommended next steps. It does not cover rate limits or failure modes, keeping it short of a 5.

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 tightly packed sentence that front-loads the action and the sources, then closes with the optional parameter. Every clause carries information; nothing is repeated or padded.

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 usefully characterizes the return as a pass/fail decision plus next steps, and the nested body object is fully documented in the schema. For a read-only single-parameter check with rich annotations, an agent has enough to invoke it correctly, though the data-source siblings' relationship remains 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 vrm and insurance_declared are already fully documented in the schema, including the askMID rationale. The description's mention of the optional yes/no value adds no syntax or meaning beyond what the schema states, so the 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?

States a specific verb ('Run the Road Legal Pass'), the resource (a UK registration), and the data sources involved (live MOT and tax from DVLA plus a declared-insurance check), with a defined outcome (pass/fail plus next steps). However, it never distinguishes itself from the near-identical sibling vehicle_check_road_legal, so an agent cannot tell the two apart from the text alone.

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?

It notes that insurance_declared may optionally be supplied as yes/no, which implies when the parameter is relevant, but it gives no explicit when-to-use guidance or exclusion relative to road_legal_catalogue, road_legal_data_sources, or vehicle_check_road_legal. Usage is left to inference.

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