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

With no annotations, the description carries the full behavioral burden and discloses two important traits: the key is shown only once and must be stored in a secret store, and creation is free. It does not cover authorization requirements or rate limits, but the security-sensitive behavior is clearly surfaced.

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 three short sentences with zero waste, front-loading the purpose and then the critical one-time visibility warning. Every sentence adds useful information.

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?

The description covers purpose, key sensitivity, and cost, but leaves the three parameters completely unexplained and does not state any auth or environment prerequisites. With no annotations and no output schema, an agent lacks enough context to invoke this tool confidently.

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 0% and the description does not mention any of the three parameters (label, payer, credit_code). It provides no meaning or format guidance for them, so an agent must guess what to supply.

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 clearly states a specific verb and resource: create a prepaid API key. It adds the qualifier 'prepaid' and mentions cost, which helps distinguish it from generic key creation, but it does not explicitly differentiate from siblings like topup_credits.

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 does not state when to use this tool versus alternatives such as topup_credits or get_pricing. Usage is only implied by the tool name and the word 'prepaid'; no explicit when/when-not guidance is provided.

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