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

Annotations already declare readOnlyHint=true, but the description adds genuinely useful context beyond them: it warns that the operation is read-only 'despite being a POST', resolving a method/verb ambiguity the agent would otherwise face. It still omits auth requirements and rate-limit behavior, but the safety profile is well covered.

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?

One dense sentence enumerating the returned fields, front-loading the primary action, followed by a short and valuable read-only note. The trailing 'Unkey: POST /v2/keys.getKey.' is mildly redundant framing but cheap and confirms the endpoint.

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 output schema, the description usefully enumerates the returned metadata fields (name, owner, permissions, credits, rate limits, enabled state). For a two-parameter read tool this is close to complete; only pagination/error or permission prerequisites are absent.

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 both parameters (keyId, decrypt) are fully documented in the schema, including the important 'NOT the secret key itself' clarification and the recoverable-key constraint on decrypt. The description adds no parameter-level detail beyond what the schema already provides, 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) and resource (a key's metadata by id) and enumerates the returned fields, so the agent knows exactly what it gets back. It does not, however, name or contrast with sibling lookups like unkey_whoami_key or unkey_get_identity, leaving sibling differentiation to inference.

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?

Usage is only implied — the agent can infer you call it when you already have a key id and need its metadata. There is no explicit when-to-use, no condition selecting it over unkey_whoami_key or unkey_list_api_keys, and no stated prerequisites.

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