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

The description adds critical behavioral details beyond the annotations: the key is shown only once, must be stored immediately, must be passed as X-Api-Key, and rate limits of 3 keys per IP per 24 hours. This is exactly the kind of non-obvious behavior an agent needs to know.

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 description is compact and front-loaded with the primary action, then provides only high-value supporting details about key handling and rate limits. Every sentence earns its place.

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 tool with an output schema and clear annotations, the description is complete: it explains what to do with the response, how to use the key subsequently, and the limitations that could affect agent behavior.

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 the email parameter is already fully described in the input schema. The description essentially restates that email is required, adding 'delivery and repeat-signup lookup' context but no new mechanical detail.

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 states a specific verb and resource: generate a DataNexus API key for an email address. It clearly distinguishes this from the related sibling tools apikeys_revoke_api_key and apikeys_rotate_api_key by defining this as the creation operation.

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 gives clear context on when to use the tool: when a caller needs a new API key for an email address, and how the key should be used afterward. It does not explicitly exclude the rotate/revoke siblings, but the purpose is unmistakable.

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