Start charging now

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

The annotations already indicate a non-read-only, idempotent command, but the description adds meaningful behavioral context: it is synchronized with the car's reported charging state, requires the car to be plugged in, and should only be issued after explicit user consent. There is no contradiction with the annotations.

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?

The description is short, front-loaded with the core action, and every sentence adds a necessary constraint or safety condition. There is no filler or redundant restatement of structured fields.

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 one-parameter command with clear annotations, the description is complete: it covers eligibility, preconditions, user-consent requirements, preview behavior, and verification against vehicle state. Nothing essential is left to guesswork.

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 schema fully documents the confirm parameter, so the baseline is met. The description adds a useful decision rule—use confirm=false for preview when in doubt—which supplements the schema without replacing it.

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?

The description names the specific action ('Start charging the plug-in battery immediately') and the resource, distinguishing it from read-only sibling tools and from schedule-based charging. Vehicle eligibility and the plugged-in requirement further pin down its scope.

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 explicitly states when to use the tool: PHEV/EV, car plugged in, and only on explicit user request. It also gives a concrete fallback instruction—'preview with confirm=false when in doubt'—which provides clear decision guidance even without a same-purpose sibling.

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