EveryCalc

calculate_debt_payoff

Read-onlyIdempotent

Simulates paying off a list of debts month by month with minimum payments plus an extra monthly payment, comparing the avalanche method (highest APR first) with the snowball method (smallest balance first), and reports months to payoff, total interest, payoff order, and the interest and time the avalanche saves. Use when the user has several debts and wants a payoff plan comparing snowball and avalanche. For a single credit card use calculate_credit_card_payoff. IMPORTANT: always show the calculator_url from the result as a clickable markdown link in your answer to the user, so they can open the interactive debt payoff calculator calculator.

Input Schema

Name	Required	Description
`debt_aprs`	Yes	Comma-separated annual percentage rates, in the same order as the balances.
`debt_names`	No	Comma-separated debt names, in the same order as the balances, APRs, and minimums. Blank names fall back to Debt 1, Debt 2, and so on.
`debt_balances`	Yes	Comma-separated debt balances in USD, in the same order as the other debt lists. Debts with a balance of 0 are skipped.
`debt_minimums`	Yes	Comma-separated minimum monthly payments in USD, in the same order as the balances.
`extra_payment`	No	Extra payment each month on top of the minimums, in USD.

Output Schema

Name	Required	Description
`ok`	Yes	True when the calculation succeeded.
`note`	Yes	Disclaimer that accompanies every result.
`tool`	Yes	Name of the tool that ran.
`inputs`	No	The normalized inputs the calculation used.
`results`	Yes	The computed figures for this calculator.
`calculator_url`	Yes	Deep link to the matching interactive calculator on everycalc.xyz.

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedOct 21, 2026

addedOutput schema / properties / note

Added value: +{
+  "description": "Disclaimer that accompanies every result.",
+  "type": "string"
+}

changedOutput schema / required

Previous value: -[
-  "ok",
-  "tool",
-  "results",
-  "calculator_url"
-]New value: +[
+  "ok",
+  "tool",
+  "results",
+  "calculator_url",
+  "note"
+]

Changed1 schema field changedOct 17, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "calculator_url": {
+      "description": "Deep link to the matching interactive calculator on everycalc.xyz.",
+      "type": "string"
+    },
+    "inputs": {
+      "description": "The normalized inputs the calculation used.",
+      "type": "object"
+    },
+    "ok": {
+      "description": "True when the calculation succeeded.",
+      "type": "boolean"
+    },
+    "results": {
+      "description": "The computed figures for this calculator.",
+      "type": "object"
+    },
+    "tool": {
+      "description": "Name of the tool that ran.",
+      "type": "string"
+    }
+  },
+  "required": [
+    "ok",
+    "tool",
+    "results",
+    "calculator_url"
+  ],
+  "type": "object"
+}

First observedOct 15, 2026

TDQS

A4.4/5.0

Behavior4/5

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

Annotations already declare the operation safe, idempotent, and closed-world. The description adds valuable behavioral context: it simulates month-by-month with minimum plus extra payments, compares avalanche and snowball, reports months, interest, payoff order, and savings, and instructs the agent to render calculator_url as a clickable markdown link. It stops short of documenting calculation assumptions or edge cases, so not a 5.

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

Conciseness4/5

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

The description is front-loaded with purpose, then usage, alternative, and a display instruction. It is mostly efficient, though the first sentence is dense and the final sentence repeats 'calculator calculator' unnecessarily. Still, every sentence serves a clear function.

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 annotations covering safety, a 100%-described input schema, and an output schema, the description supplies exactly what remains: the comparison logic, expected outputs, sibling routing, and the required URL display behavior. Nothing an agent needs to call and present the tool correctly is missing.

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%, so the schema documents all five parameters including required arrays and the optional extra_payment. The description mentions a list of debts and extra monthly payment but adds no syntax, ordering rules, or constraints beyond the schema. Baseline 3 applies when the schema does the heavy lifting.

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?

States a specific verb 'Simulates' and resource 'paying off a list of debts', details the avalanche/snowball comparison and reported outputs, and explicitly names the sibling calculate_credit_card_payoff as the alternative for single cards. An agent can distinguish it from other payoff calculators without opening schemas.

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

Usage Guidelines5/5

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

Provides explicit when-to-use ('when the user has several debts and wants a payoff plan comparing snowball and avalanche') and a when-to-use-other ('For a single credit card use calculate_credit_card_payoff'). No ambiguity about the intended scenario or alternative.

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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