finance.amortize

Compute a loan or mortgage amortization schedule. Pass principal, annualRatePct (e.g. 6.5), and the term as termMonths or termYears; optional extraMonthly adds extra principal each month (shortening the term). Returns the fixed monthly payment, total interest, total paid, the actual payoff month count, and the full month-by-month schedule (each row: payment, principal, interest, remaining balance). Handles the 0% case and trims the final payment exactly. Deterministic — the ground-truth answer for a loan/mortgage/auto-finance question instead of an LLM approximating compound interest. No external calls.

price

$0.0010 USDC per call

method

GET/api/finance/amortize

payment

x402 v2 · USDC on Base (EIP-3009) or Solana (SPL transfer)

auth

None. Sign the payment, retry with PAYMENT-SIGNATURE.

tier

Tier 0 — no paid upstream

Parameters

Name	Type	Description
`principal`required	number
`annualRatePct`required	number
`termMonths`	integer	min 1 · max 1200
`termYears`	number	min 0 · max 100
`extraMonthly`	number	min 0

Code samples

cURLbash

# 1. Probe with no auth → 402 envelope with PaymentRequirements
curl -sS 'https://2s.io/api/finance/amortize?principal=1&annualRatePct=1&termMonths=1&termYears=0&extraMonthly=0'

# 2. Sign + retry with PAYMENT-SIGNATURE:
curl -sS 'https://2s.io/api/finance/amortize?principal=1&annualRatePct=1&termMonths=1&termYears=0&extraMonthly=0' \
  -H 'PAYMENT-SIGNATURE: <base64-json-payload>'

# Or use the canonical runner (handles probe → sign → retry):
#   EVM_PRIVATE_KEY=0x... node --env-file=.env.local \
#     --experimental-strip-types scripts/x402-pay.ts \
#     'https://2s.io/api/finance/amortize?principal=1&annualRatePct=1&termMonths=1&termYears=0&extraMonthly=0'

TypeScript / Node — @2sio/sdktypescript

import { TwoS } from '@2sio/sdk'

const client = new TwoS({
  privateKey: process.env.EVM_PRIVATE_KEY as `0x${string}`,
})

const result = await client.finance.amortize({
  "principal": 1,
  "annualRatePct": 1,
  "termMonths": 1,
  "termYears": 0,
  "extraMonthly": 0
})

console.log('endpoint:', result.endpoint)
console.log('cost:', result.costUsd, 'USDC')
console.log('tx:', result.settlement?.txHash)
console.log('data:', result.data)

Python — 2siopython

import os
from twosio import TwoS

client = TwoS(private_key=os.environ["EVM_PRIVATE_KEY"])

result = client.finance.amortize(principal=1, annualRatePct=1, termMonths=1, termYears=0, extraMonthly=0)

print("endpoint:", result.endpoint)
print("cost:", result.cost_usd, "USDC")
print("tx:", (result.settlement or {}).get("tx_hash"))
print("data:", result.data)

MCP — Claude Desktop / AgentKit / any MCP hostjson

// 1. Add @2sio/mcp to your MCP host config (Claude Desktop example below).
//    EVM_PRIVATE_KEY funds x402 payments per call.

// claude_desktop_config.json
{
  "mcpServers": {
    "2sio": {
      "command": "npx",
      "args": ["-y", "@2sio/mcp"],
      "env": { "EVM_PRIVATE_KEY": "0x..." }
    }
  }
}

// 2. Once the server is running, agents call this tool via standard MCP:

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "finance.amortize",
    "arguments": {
      "principal": 1,
      "annualRatePct": 1,
      "termMonths": 1,
      "termYears": 0,
      "extraMonthly": 0
    }
  }
}

Response

Field	Type	Description
`ok`	boolean	one of: true
`items`	array
`total`	integer	Total matching rows upstream; null when unknown.
`source`	object

Example response datajson

{
  "ok": true,
  "items": [
    {
      "principal": 1,
      "annualRatePct": 1,
      "termMonths": 1,
      "monthlyRate": 1,
      "monthlyPayment": 1,
      "extraMonthly": 1,
      "payoffMonths": 1,
      "totalInterest": 1,
      "totalPaid": 1,
      "schedule": [
        {
          "month": 1,
          "payment": 1,
          "principal": 1,
          "interest": 1,
          "balance": 1
        }
      ]
    }
  ],
  "total": 1,
  "source": {
    "provider": "example",
    "url": "example",
    "license": "example"
  }
}

Discovery

/api/directory — full catalog of every endpoint
/openapi.json — OpenAPI 3.1 spec (per-op x-payment-info, x402Payment security)
/.well-known/x402 — machine-readable service descriptor for x402-aware crawlers
/.well-known/mcp/server-card.json — MCP SEP-1649 server card
/llms.txt — plain-text manifest for LLM ingestion

2s.io is x402-native. Every call is paid per-request from a USDC-funded EVM wallet on Base — no signup, no API keys, no monthly fees. Source code: github.com/2s-io/sdk.