# LogiGrain API
> Deterministic calculation APIs for AI agents. Pay-per-call via x402 protocol.

## Overview
LogiGrain provides 12 stateless calculation endpoints optimized for AI agent consumption.
All endpoints require x402 micropayment ($0.001 USDC per call) on Base mainnet.
Add ?test=true to bypass payment for testing.

## Network
- Protocol: x402 v2
- Network: Base mainnet (eip155:8453)
- Asset: USDC (0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913)
- Price: $0.001 per call
- Facilitator: CDP (api.cdp.coinbase.com)

## Endpoints

### /api/compound
Compound interest calculator.
Params: principal (number), rate (percent), years (integer), monthly (optional number)
Example: /api/compound?principal=10000&rate=7&years=20

### /api/convert
Currency exchange rate conversion.
Params: from (currency code), to (currency code), amount (number, default 1)
Example: /api/convert?from=USD&to=JPY&amount=100

### /api/convert-unit
Physical unit conversion (length, weight, speed, data, area, volume, energy, temperature).
Params: value (number), from (unit), to (unit), category (optional)
Example: /api/convert-unit?value=100&from=kilometer&to=mile

### /api/json
JSON validation, formatting, and analysis.
Params: action (validate|format|minify), input (JSON string)
Example: /api/json?action=format&input={"key":"value"}

### /api/math
Safe mathematical expression evaluator with functions and variables.
Params: expr (expression), vars (optional, comma-separated key=value)
Example: /api/math?expr=sqrt(144)+2^10

### /api/code
Syntax validation for JSON, JavaScript, HTML, CSS.
Params: lang (json|javascript|html|css), code (source code)
Example: /api/code?lang=json&code={"key":"value"}

### /api/feed
Real-time forex and cryptocurrency price feeds.
Params: type (forex|crypto), symbols (comma-separated), base (optional, for forex)
Example: /api/feed?type=crypto&symbols=BTC,ETH

### /api/date
Date calculations: diff, add, unix timestamp, business days.
Params: action (diff|add|unix|business), start, end, days, timestamp
Example: /api/date?action=diff&start=2026-01-01&end=2026-12-31

### /api/probability
Bayesian inference, combinations, and permutations.
Params: type (bayes|combination|permutation), pa, pba, pbna, n, r
Example: /api/probability?type=bayes&pa=0.01&pba=0.9&pbna=0.05

### /api/token-cost
LLM API cost estimator comparing major models.
Params: input (tokens), output (tokens), requests (per day)
Example: /api/token-cost?input=1000&output=500&requests=100

### /api/era
Japanese era (和暦) converter: ISO↔era, fiscal year.
Params: action (to_iso|to_era|fiscal_year), value
Example: /api/era?action=to_iso&value=R6

### /api/moon
Lunar phase calculator with Japanese moon culture trivia.
Params: date (YYYY-MM-DD, optional), tz (timezone), include (trivia)
Example: /api/moon?include=trivia&tz=Asia/Tokyo

## Documentation
- OpenAPI: https://logigrain.net/openapi.json
- x402 Payment Info: https://logigrain.net/.well-known/x402.json