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

Annotations already declare this is a read-only, idempotent, non-destructive, closed-world read. The description adds value beyond them by disclosing the auth precondition (RegTail account must be linked) and the fact that unlock windows carry an expiry. It does not discuss rate limits or freshness of the 'recent checks' list.

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?

Roughly two sentences, front-loaded with what is returned, followed by the motive and the prerequisite. Slightly circuitous in the clause about picking up a previously checked car, but no sentence is wasted.

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?

An output schema exists, so return values need not be restated, and with no parameters there is little else to specify. The description covers the auth prerequisite and the data shape, leaving only minor gaps such as how many recent checks are returned.

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?

The tool takes zero parameters, which is the baseline-4 case. Nothing further is needed from the description about argument semantics.

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 the specific resources returned: the cars the user has unlocked (with unlock expiry) plus their recent checks. That is a concrete retrieval purpose distinguishable from write-oriented siblings like unlock_report and decode_plate. It does not, however, explicitly differentiate itself from similar retrieval siblings such as free_check or sample_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?

Gives an implied use case ('so a conversation can pick up a car checked earlier') and a prerequisite ('Needs the user's RegTail account linked'). It stops short of naming when a sibling like full_report or free_check would be the better choice, so the routing guidance is only implied.

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