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: the operation is read-only despite being issued as a POST, and it maps to the vendor endpoint POST /v2/apis.getApi. That prevents an agent from treating the HTTP method as a mutation signal. It stops short of describing return shape or error behavior.

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 with zero waste, front-loading what the tool fetches before the behavioral caveat.

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 single-parameter read-only lookup whose safety profile is covered by annotations and whose return values are not schematized, the description is essentially complete. A brief note on what the returned namespace contains would push it to a 5.

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?

Only one parameter (apiId) exists and the schema already documents it at 100% coverage, including the api_ prefix format. The description's 'by id' adds nothing beyond the schema, so the baseline of 3 is appropriate.

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 ('API namespace') plus the lookup key ('by id'). This is clearly distinct from sibling getters like unkey_get_identity and unkey_get_key.

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 implied by the name and the 'fetch by id' framing, and the note about it being a read-only POST helps an agent not misclassify it. However, there is no explicit when-to-use versus alternatives such as unkey_list_api_keys or unkey_get_key.

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