calculate_with_extra_payments

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

With no annotations, the description carries the full burden. It does disclose the core behavioral mechanic (extra payment applied for a limited window, then reverting to base payment), which is genuinely useful. It does not, however, address edge cases such as extra payments exceeding the remaining balance or invalid input combinations, nor confirm the operation is a pure non-mutating calculation.

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 purpose sentence is front-loaded, followed by a well-organized Args block that maps one-to-one onto the parameters. There is little filler; the Returns line is arguably redundant given an output schema exists, but the overall structure is clean.

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 six-parameter calculation tool with no annotations but a present output schema, the description covers purpose, mechanism, and every parameter. Return-value explanation is correctly left to the output schema. Only the absence of any sibling-routing guidance keeps it from being fully complete.

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%, so the description must compensate, and it does: all six parameters are documented with units and intent (dollars for principal and payments, percentage for the rate, months for the extra period). Minor gaps remain — no constraints on ranges or the relationship between monthly_payment and extra_monthly_payment.

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 specific verb and resource ('Calculate accelerated payoff from extra monthly payments for a fixed period') and describes the mechanism, making the tool's purpose clear. However, it never distinguishes itself from closely related siblings like calculate_with_lump_sum or compare_loan_scenarios, so an agent must infer the boundary.

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 mechanism description ('extra amount is added to every payment for the first num_months_with_extra months, then reverts to base payment') implies the scenario this tool fits, but there is no explicit when-to-use guidance and no mention of the alternative tools for lump-sum or scenario comparison. Usage is inferable but not stated.

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