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

Beyond the readOnly/idempotent/non-destructive annotations, the description discloses that it consumes no credits, that it requires a linked account, and that a locked plate yields unlocked=false with a message. These are real operational traits an agent cannot infer from annotations or schema.

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?

Purpose and scope are front-loaded, and the guidance sentences are tight and action-oriented. The content enumeration is long, but each listed section is meaningful to an agent deciding whether this tool answers the user's question.

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?

Prerequisites, cost model, and the locked-plate error path are all covered, and an output schema exists so return values need no prose. Nothing an agent needs before invoking or after a failed call 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?

Only one parameter (plate) and schema coverage is 100%, with the schema itself documenting spacing/case tolerance and an example. The description adds no syntax or format detail beyond that, 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?

Opens with a specific verb+resource ('The full report of a car the user has unlocked') and then enumerates exactly what the report contains (verdict, MOT tests, mileage analysis, advert claims, viewing checklist). This clearly separates it from siblings like free_check, sample_report, and unlock_report.

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?

States the use case ('Use to discuss a car in depth'), the prerequisite (RegTail account linked), the cost behavior ('Never spends'), and the exact failure path plus the follow-up action (ask the user before calling unlock_report). Alternatives and conditions are explicit.

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