financial-calculators

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 mark the tool as read-only and idempotent, so no side-effect disclosure is needed. The description adds value by exposing the error case for an insufficient payment and signaling that results are approximate ('about 32 months'), which is useful behavioral context beyond the annotations.

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?

The description is compact: one purpose sentence, one example, and one error condition. The main action is front-loaded, and there is no filler or redundant restating of the title.

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?

With full schema coverage, a read-only/idempotent annotation profile, and an existing output schema, the description is sufficient for an agent to select and invoke the tool correctly. The example and error condition round out the remaining context.

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

Parameters3/5

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

Schema description coverage is 100%, and the input schema already documents every parameter, including the payment constraint and the meaning of purchases. The example in the description adds concrete numeric grounding, but it does not substantially change or extend the parameter semantics.

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 states a specific verb and resource: 'Calculate how long it takes to clear a credit card balance...' followed by the two outputs (months and total interest paid). The worked example makes the purpose concrete and clearly separates it from sibling calculators like compound_interest or compare_investments.

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

Usage Guidelines4/5

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

The description gives clear usage context: fixed monthly payment, APR, and balance payoff, plus an explicit failure condition when payment is too low. It does not explicitly name sibling alternatives or say when not to use the tool, so it just misses the top score.

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

All financial-calculators tools Inspect

Try in Browser

RayrunBuild, deploy, and operate MCP servers without becoming an infrastructure team.ray.runAd

Glama MCP Gateway

Add one secure layer between your agents and this server.

TDQS

A4/5.0

Disambiguation4/5

Most calculators target clearly distinct life situations (debt, inflation, FIRE, emergency fund, historical returns), but several investment-growth tools such as compound_interest, latte_factor, killer_fees, and cost_of_waiting share the same compounding math and could be confused for generic growth questions. Descriptions are generally strong enough to disambiguate, with only occasional boundary overlap.

Naming Consistency4/5

Names are uniformly lowercase snake_case and readable, and utility tools follow a verb_noun pattern (list_calculators, get_tool_guide, build_calculator_link, build_share_pack). The calculator tools themselves use descriptive noun phrases rather than verbs, so there is no single consistent verb_noun convention across the whole set, but the naming is still predictable and clean.

Tool Count5/5

With 14 tools, the server sits comfortably in the ideal 3-15 range. Ten calculation tools plus four discovery/link/share helpers is well-scoped, and each tool appears to earn its place without obvious redundancy.

Completeness4/5

Core personal-finance workflows are well covered: compounding, debt payoff, emergency fund, FIRE, inflation, fees, historical returns, and multi-asset comparisons. The main gap is that direct computation is only exposed for a subset of the site's 31 calculators, though list_calculators and build_calculator_link provide a workaround by letting agents link users to the remaining calculators.

Resources

Need Help?