calculate_minimum_payment_trap

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

Annotations already declare the tool as read-only, idempotent, and non-destructive. The description adds valuable behavioral context by clearly stating the core assumption ('pays exactly the listed minimum every month with no extra') and the return type ('payoff timeline'), which are crucial for interpretation and go beyond annotation hints.

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 only three sentences, with the core purpose front-loaded in the first sentence. Every sentence contributes a distinct piece of information (purpose, assumption, significance), and there is no redundancy or fluff, making it highly concise and well-structured.

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, read-only calculation tool with well-documented inputs and no output schema, the description covers the essential context: scope (single card), the assumed payment behavior, and the type of result (payoff timeline). It could be more explicit about the exact fields of the payoff timeline (e.g., total interest paid, months to payoff), but it is sufficiently complete for the tool's simplicity.

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?

The input schema already provides 100% coverage of all three parameters with clear descriptions and units (USD, APR percent, monthly minimum). The description reinforces the meaning of minimum_payment through the 'exactly the listed minimum' phrasing but does not add new parameter-level detail, so it remains at the baseline for full schema coverage.

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 function with a specific verb ('Show the cost') and resource ('single credit card or revolving debt'), making its purpose unmistakable. It also distinguishes itself from siblings by focusing specifically on minimum-payment scenarios and the no-extra assumption, which sets it apart from general payoff calculators.

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 implies a clear use case ('Critical for showing the cost of carrying credit card debt at high APRs') and scopes to a single credit card or revolving debt, which helps differentiate from sibling tools like calculate_debt_payoff or compare_snowball_vs_avalanche. However, it does not explicitly mention when not to use this tool or name alternative tools, so there is room for more direct exclusions.

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