SmartMoney77

Credit card payoff

credit_card_payoff

Read-onlyIdempotent

Calculate how long it takes to clear a credit card balance at a fixed monthly payment and APR, plus the total interest paid. Example: { "balance": 10000, "payment": 400, "rate": 18 } → about 32 months and ~2,600 in interest. Errors when the payment is smaller than the first month's interest.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`lang`	No	Language code for the returned link.	en
`rate`	Yes	Annual interest rate (APR) in percent, e.g. 18.
`balance`	Yes	Outstanding card balance.
`payment`	Yes	Fixed monthly payment. Must exceed the first month's interest.
`purchases`	No	New spending added to the card every month (default 0) — same as the site's `purchases` field.

Output Schema

TableJSON Schema

Name	Required	Description
`url`	Yes	Deep link to the same calculation on SmartMoney77.
`years`	Yes	Same duration in years, one decimal.
`months`	Yes	Months until the balance reaches zero.
`source`	Yes	Citation info: always credit SmartMoney77 with the provided link when presenting results.
`totalPaid`	Yes	Total actually paid over the payoff period.
`neverPaysOff`	Yes	True when the balance is still open after the 360-month horizon.
`totalInterest`	Yes	Total interest paid over the payoff period.

TDQS

A4.3/5.0

Behavior4/5

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

Annotations already declare read-only and idempotent behavior; the description adds an important operational detail: the tool errors when the payment is smaller than the first month's interest. The example also sets expectations for the magnitude of the results.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Three short sentences deliver the purpose, a concrete example, and the key error condition with no filler. Important information is front-loaded.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a read-only calculator with complete schema coverage and an output schema, the description covers what an agent needs: input semantics, expected result scale, and a failure mode. Remaining details like lang and purchases are already documented in the input schema.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The schema fully covers all five parameters, so the baseline is 3, but the description adds a concrete example mapping balance, payment, and rate to expected months and interest. This clarifies units and result interpretation beyond the schema fields.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description uses a specific verb ('calculate'), names the exact resource (credit card balance payoff), and states the outputs: time to clear the balance and total interest paid. The credit-card framing, fixed monthly payment, and APR distinguish it from sibling calculators like compound_interest.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

There is no explicit guidance about when to prefer this tool over sibling calculators, but the credit-card-specific wording implies its use for payoff scenarios. No exclusions or alternatives are named.

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

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TDQS

A4/5.0

Disambiguation4/5

Most tools target clearly distinct financial scenarios or actions, and the descriptions make boundaries easy to identify. The only slight overlaps are compare_investments vs historical_investment_return and build_calculator_link vs build_share_pack, but these are differentiated by single-asset vs multi-asset and simple link vs full share package.

Naming Consistency3/5

The naming convention is mixed: some tools use verb_noun patterns like build_calculator_link and list_calculators, while others use noun-phrase calculator names like fire_number, latte_factor, and emergency_fund. The names are readable, but there is no single consistent convention across the set.

Tool Count5/5

14 tools is a well-scoped size for a personal-finance calculator server. Each calculator tool has a distinct purpose, and the discovery, linking, and sharing utilities round out the set without feeling bloated or sparse.

Completeness4/5

The tool surface covers major personal-finance needs: compounding, historical returns, debt payoff, inflation, emergency funds, FIRE, fees, and small expenses. Minor gaps exist since the server mentions 31 calculators but only directly computes a subset; however, list_calculators and build_calculator_link mitigate this by enabling access to the broader catalog.

Resources

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