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

The annotation already declares readOnlyHint=true, but the description adds the genuinely non-obvious disclosure that the underlying call is a POST yet still read-only — exactly the kind of transport quirk an agent would otherwise get wrong. It also names the raw endpoint (POST /v2/apis.getApi) for direct API callers.

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 sentences, front-loaded with the core action, followed by the behavioral caveat and the endpoint mapping. No filler.

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 one-parameter read tool with annotations covering safety, the description is essentially sufficient. The only omission is any hint at the response shape (no output schema exists), which is minor for a single-resource fetch.

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?

Schema coverage is 100% and the single apiId parameter is fully documented in the schema with its format (api_...). The description only restates the lookup-by-id behavior, so 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?

States a specific verb (fetch) plus resource (API namespace) and the lookup key (by id), which cleanly separates it from unkey_create_api and the unkey_list_* siblings. An agent can identify the operation without opening the 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?

'by id' implies the preconditions (you must already have an api_... identifier), and the sibling set contains no other single-API getter to disambiguate against. There is no explicit when-to-use or when-not-to-use statement, 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.