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

Annotations cover the safety profile (not read-only, not idempotent, not destructive), and the description adds a genuinely non-derivable behavior: the secret is returned only once and cannot be retrieved again. The instruction to tell the user to store it securely is actionable operational context. It does not mention rate limits or whether creating a key revokes prior keys, but for a short tool this is strong disclosure.

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, zero filler, with the one-time secret caveat placed second where it is most likely to be acted on. Nothing is repeated from the schema or title.

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?

No output schema exists, and the description does the important job of explaining what the caller receives (a one-time secret). The remaining gap is the parameter relationship between scope and sending_domain_id, which the description leaves to the schema.

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 67% -- 'scope' and 'sending_domain_id' are documented in the schema with enums and constraints, but 'name' has no description anywhere. The description adds nothing about the required name field or how scope interacts with sending_domain_id (e.g., that a domain lock only makes sense for a sending key). Mid-range baseline 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 and resource ('Create an API key') that unambiguously separates it from get-api-key, list-api-keys, regenerate-api-key and update-api-key in the sibling set. It does not explicitly name those alternatives, so it stops just short of full sibling differentiation.

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?

There is no guidance on when to create a fresh key versus regenerating or updating an existing one, and no mention of prerequisites such as workspace permissions or scope choice. The agent must infer usage entirely from the name.

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