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

No annotations are provided, so the description carries the full burden of behavioral disclosure. The description mentions outputs (monthly payment, total interest, months saved) but doesn't disclose key behaviors: whether it assumes a fixed interest rate, whether it compounds monthly, whether extra payments are applied to principal, or what the default term is (though the schema hints at a default of 10 years). It also doesn't state whether the calculation is an estimate or exact, or any limitations. For a financial calculation tool, this is a significant gap.

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 concise sentence that front-loads the core purpose ('Student loan payoff') and lists the key outputs. It's efficient with no wasted words. However, it could be slightly more structured by separating the purpose from the outputs, but it's still appropriately sized.

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 4 parameters, no output schema, no annotations), the description is incomplete. It doesn't explain the calculation assumptions (e.g., fixed vs variable rate, compounding frequency, whether extra payments reduce principal), nor does it describe the return format. An agent would need to infer these details or call the tool to discover them. For a financial tool, this is a notable gap.

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%, so the schema already documents all four parameters. The description adds context by mentioning 'extra payments' which maps to the extraPayment parameter, and 'months saved' implies the loanTermYears parameter. However, it doesn't add meaning beyond what the schema provides, such as clarifying that interestRate is an annual percentage or that loanAmount is in dollars. Baseline 3 is appropriate given 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 states a clear verb and resource: 'Student loan payoff' with specific outputs (monthly payment, total interest, months saved with extra payments). It distinguishes itself from sibling calculators like calculate_car_loan and calculate_mortgage by explicitly naming student loans. However, it doesn't explicitly differentiate from other loan calculators beyond the domain, so it's clear but not fully differentiated.

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 usage context: it's for student loan payoff calculations, and the mention of 'extra payments' suggests a scenario where the user wants to compare payoff timelines. However, it doesn't explicitly state when to use this tool versus alternatives like calculate_mortgage or calculate_car_loan, nor does it provide exclusions or prerequisites. The context is implied but not explicit.

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