# ZARONIA Verify — independent SA FRN & money-market coupon verification

No account. No API key. No signup. Pay per call with x402.

Recompute and verify ZARONIA-linked coupons against the SARB Compounded
ZARONIA Index, with full workings and an audit verdict per calculation.
Engines match bank/BESA acceptance vectors to 4dp; verdicts at 0.05bp tolerance.

## Sources & licence
Computed exclusively against the SARB Compounded ZARONIA Index as published
by the South African Reserve Bank (ingested each business day); every response
shows the observation dates, index values and formula used — a full audit trail.
Independent service, not affiliated with the SARB or any government.

## How to call a paid endpoint (x402)
1. Call the endpoint with no payment. You get HTTP 402. The payment challenge is in the
   base64-encoded `payment-required` RESPONSE HEADER (the body is an empty `{}`); decode it to see
   price, asset (USDC), network (eip155:8453 = Base) and pay-to address.
2. Sign the payment with any x402 client — @x402/fetch wraps fetch and does
   steps 1-3 automatically.
3. Retry with the signed X-PAYMENT header. You get HTTP 200 + the verdict;
   the settlement receipt is returned in the PAYMENT-RESPONSE header.
Bad input is rejected FREE (4xx before the payment gate) — you never pay to fail.
Free, no payment: https://api.zaroniacalculator.co.za/v1/conventions · https://api.zaroniacalculator.co.za/v1/integrity · https://api.zaroniacalculator.co.za/v1/index/latest · https://api.zaroniacalculator.co.za/openapi.json

## Verify the index before you pay for anything
GET https://api.zaroniacalculator.co.za/v1/integrity (free) returns the result of two checks that actually ran:
1. Compounding SARB's published daily ZARONIA rates reproduces SARB's published index.
2. Every index value served is identical to the value SARB published.
The full history is re-verified weekly; the recent tail on every daily ingest.
The index recurrence is published in full at https://api.zaroniacalculator.co.za/v1/conventions so you can reproduce it yourself.

## Pricing ladder
- $0.005 — one SARB Compounded ZARONIA Index point · $0.02 index range
- $0.10 — OTC money-market coupon verification
- $0.25 — listed-FRN coupon verification (SARB §2.2.3, full workings + verdict)
- $1.00 — portfolio run (≤10 instruments, per-instrument verdicts)
Licensed tiers (bank live-pulls, file feeds, unlimited): api@3l-groupconsulting.co.za

## Endpoints
POST /v1/verify/frn  { calc_date, issue_date, first_coupon_date, coupon_frequency, margin_pct, lookback_bdays?, expected_coupon_pct? }
POST /v1/verify/otc  { settlement_date, margin_pct, expected_coupon_pct? }
POST /v1/verify/portfolio  { instruments: [ { type: listed_frn|otc_money_market, ... } ] }
GET  /v1/index/{date} · GET /v1/index?from=&to=

## Machine-readable discovery
- x402 resource map: https://api.zaroniacalculator.co.za/.well-known/x402.json
- Agent card: https://api.zaroniacalculator.co.za/.well-known/agent.json
- OpenAPI: https://api.zaroniacalculator.co.za/openapi.json
- MCP server (streamable HTTP): https://api.zaroniacalculator.co.za/mcp