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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered structurally. The description adds a real prerequisite beyond them: 'Needs the user's RegTail account linked,' which tells the agent an auth precondition must be met before calling. It stops short of describing return shape or pagination, but the output schema carries that.

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 short sentences, front-loaded with the return content and followed by the prerequisite. Every clause earns its place. Slightly compressed phrasing ('with when each unlock ends') costs a little polish but not clarity.

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 parameters, full annotation coverage, and an output schema that defines the return values, the description only needs to say what the tool is for and any preconditions. It does both, adding the account-linking requirement. The only gap is sibling differentiation, which matters given seven related tools.

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, so there is nothing for the description to disambiguate. Baseline for a no-param tool is 4, and nothing in the text confuses the (empty) argument surface.

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 specifically what it returns: the user's unlocked cars with each unlock's end time, plus their recent checks. That is a concrete resource and scope an agent can act on. It does not, however, differentiate itself from siblings like unlock_report or full_report, so an agent cannot route on the description 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?

The phrase 'so a conversation can pick up a car checked earlier' gives an implied use case, which is better than nothing. But there is no explicit when-to-use rule, no when-not-to-use, and no named alternative among the seven siblings, so the selection decision 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.