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

Annotations declare readOnlyHint=false and idempotentHint=false, so mutation and non-idempotency are already covered. The description adds context beyond that: the `token` is returned only in this response, which tells the agent the value cannot be retrieved later; and it notes the caller must hold a full_access key, which is an auth requirement not visible in the schema or 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?

Three short, front-loaded sentences. The single-use token warning comes early where an agent will see it. The trailing API/operationId metadata is boilerplate but not disruptive.

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?

There is no output schema, and the description covers the most important return-value fact (the token is shown once and never again), plus the auth prerequisite. It is nearly complete for a three-parameter creation tool on a public API; only the permission/name parameter semantics 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 description coverage is only 33% (only domain_id is documented, including the full_access incompatibility), so the description should compensate for `name` and `permission`, but it says nothing about them. Its mention of full_access describes the caller's own credential, not the `permission` parameter's accepted values or default, so the gap remains.

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 uses a specific verb and resource ('Create an API key'), which is clearly distinct from list_api_keys and delete_api_key in the sibling set. It does not explicitly name those siblings, so it falls short of a 5, but an agent can identify the operation immediately.

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 states a prerequisite ('Requires a full_access API key'), which is genuinely useful for gating the call, but gives no guidance on when to choose this over alternatives or when not to create a key. Usage is implied rather than directed.

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