true_credit_cost

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

Annotations indicate readOnlyHint=true, confirming this is a safe read operation. The description adds valuable context beyond annotations by stating the tool 'Cuts through misleading '0% financing' or low-rate marketing to show actual cost,' which clarifies its analytical purpose and behavioral intent. It does not contradict annotations, as 'find' aligns with read-only behavior.

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 appropriately sized and front-loaded, with the first sentence stating the core purpose. Subsequent sentences efficiently elaborate on scope and value without redundancy. Every sentence adds value, such as listing product types and highlighting the tool's ability to reveal hidden costs, making it 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?

Given the tool's complexity (financial calculation with 5 parameters), the description is complete enough. It clearly defines the tool's purpose, usage context, and behavioral insight. With annotations covering safety (readOnlyHint=true), 100% schema description coverage, and an output schema present (which handles return values), no additional details are needed in the description for effective use.

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 100%, meaning all parameters are well-documented in the schema itself. The description does not add specific meaning or examples for parameters beyond what the schema provides, such as explaining how 'annual_late_fee' impacts calculations. With high schema coverage, the baseline score of 3 is appropriate, as the description relies on the schema for parameter details.

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 purpose: 'Find the true total cost and implied APR of any credit product.' It specifies the verb ('find') and resource ('true total cost and implied APR'), and distinguishes itself from siblings by focusing on revealing actual costs through specific examples (car financing, BNPL, etc.), unlike tools like 'compound_interest' or 'loan_comparison'.

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 provides clear context for when to use this tool: 'Works for car financing, buy-now-pay-later, credit card minimum payments, personal loans, and any fixed payment schedule.' It implies usage by listing applicable scenarios but does not explicitly state when not to use it or name alternatives among siblings, such as 'loan_comparison' for comparing loans directly.

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