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

With readOnlyHint=true already declaring the safety profile, the description still adds real context: it discloses that the call validates the root key's validity, not just network reachability, and that it is a GET with no mutation semantics. It does not mention rate limits or failure behavior, which would be the remaining gap.

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?

Three short, front-loaded sentences with no filler; the operative content ('reachable and the root key works') leads. The trailing 'Unkey: GET /v2/liveness.' partly repeats the tool name and adds little an agent cannot infer, costing it a point.

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 trivial zero-parameter tool this is close to sufficient, but no output schema exists, so the description carries the burden of explaining the response and it does not: an agent cannot tell whether success returns a boolean, a status object, or simply an HTTP 200. What is checked is clear; what comes back is not.

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 per the rubric the baseline is 4. There is nothing for the description to disambiguate, and it does not falsely imply any inputs.

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 a specific verb (check) and precise subject matter (API reachability plus root-key validity) rather than restating the title 'Check API health'. It is unmistakably distinct from all CRUD siblings such as unkey_get_key or unkey_create_api, which an agent can see without opening any schema.

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 implies diagnostic usage ('reachable', 'root key works') and hints at minimal scope with 'The only GET in the v2 surface', but never states when an agent should call it (e.g., before a batch of calls, or to validate credentials after a 401). No alternatives or exclusions are offered, so usage is only implied.

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