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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety is fully covered. The description adds the default threshold (30 days) and the fact that results are filtered by expiry window, which is genuine context, but it says nothing about rate limits, whether MOT data is refreshed live, or what the report looks like.

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?

Two tight sentences, no filler, with the core action and scope stated first and the parameter hints second. Every clause carries information.

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 read-only, fully-annotated tool with complete schema coverage and no output schema, the description covers purpose, input shape and the threshold default well enough to call it correctly. It stops short of describing the returned report structure, which matters slightly since no output schema exists.

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 schema already documents vrm, the 1-10 array bounds and the 1-365 threshold range with its default. The description restates the shape ('array of objects with a vrm each') and the threshold default without adding format or edge-case detail, so 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 and resource: check multiple UK registrations for tax/MOT expiry against a day threshold. The 'several... at once' framing implicitly separates it from the single-vehicle siblings (vehicle_lookup, vehicle_check_road_legal), but those tools are never named, so the distinction requires inference.

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?

Usage is implied by 'check several UK registrations at once', suggesting batch use over single lookups, and the default threshold is given. There is no explicit when-not guidance, no mention of the 1-10 batch limit as a selection constraint, and no named alternative for single-vehicle or broader road-legality checks.

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