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

The description discloses that the balance is credited after Stripe payment confirmation, indicating asynchronous behavior. It also states 'Free to call,' implying no cost. However, no annotations are provided, and the description does not cover error handling, reversibility, or authorization requirements.

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 a single sentence that front-loads the action and includes key details (amount, card source, timing, cost). No unnecessary words.

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 simple tool with no parameters and no output schema, the description covers the essential information: what it does, the amount, the payment method, the credit timing, and cost. It could mention failure scenarios but is adequate.

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?

Input schema has no parameters, so description does not need to add parameter details. The description implies the saved card is used, which is sufficient context.

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 the tool's action: charging a saved card $5 and crediting the balance after payment confirmation. It is distinct from sibling tools like add_funds_10 and add_funds_20 by specifying the exact amount.

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?

No guidance is provided on when to use this tool over alternatives like add_funds_10 or add_funds_20. The description does not mention any criteria for choosing the $5 amount versus other increments.

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