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

No annotations are supplied, so the description carries the full burden, and it does most of that work: the key is usable immediately for reads at a small daily quota, verifying an email raises the quota and allows contributions, and one verified email owns all its keys. It leaves out what the call actually returns (presumably key material) and whether keys can be revoked, which keeps it below a 5.

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?

The text is front-loaded with the action and the usage constraint, and nearly every clause adds information. The closing "the key works at once" repeats the earlier "works immediately for reads", a small redundancy in an otherwise tight paragraph.

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 3-parameter registration tool with no annotations and no output schema, the description covers the immediate effect, the quota and contributions gating, the email verification flow, and the ownership rule. The only minor gap is that the return value is not described.

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%, with email and agent_name already documented in the schema; the description adds useful meaning to email by explaining that it is the operator's address and that a 6-digit code is mailed and confirmed with verify. The label parameter is explained by the schema in neither place, so full compensation is incomplete.

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 first sentence, "Create an API key," states a concrete verb and resource, and the description immediately distinguishes this tool from its close siblings by naming link_email and verify as the follow-on steps. An agent can tell what this tool produces 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?

The description states an explicit exclusion ("Use this only if you have no key yet") and names alternatives for the email path ("call link_email later", "confirming it with verify"). Both the when-to-use and the when-not-to-use conditions appear in the text in plain terms.

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