Arithmetic expression evaluator (+ - * / % ^ and parentheses). GET /calc?expr=(2%2B3)*4 → {result}. Deterministic JSON, instant, no code execution.

Compound interest calculator. GET /compound-interest?principal=10000&rate=5&years=10&compoundsPerYear=12 → final amount + interest earned. Deterministic JSON, instant.

DNS lookup. GET /dns-lookup?domain=example.com&type=A|AAAA|MX|TXT|NS|CNAME|SOA → records as JSON. Live authoritative data, instant.

Every distinct Binance/Bybit/Hyperliquid exchange-pair funding-rate spread per symbol (not just the single highest-vs-lowest pair), sorted by annualized bps divergence descending, with short(high-funding venue)/long(low-funding venue) direction per pair. GET /funding-rate-arb (top20 across all symbols) or /funding-rate-arb?symbol=BTC (all pairs for that symbol) → JSON. Pure arithmetic on the same cached data as /funding-rates, $0 marginal cost, 60s cache.

Perp funding rates across Binance/Bybit/Hyperliquid, normalized to 8h-equivalent, plus cross-exchange divergence (annualized bps, top20 arbitrage signal). GET /funding-rates or /funding-rates?symbol=BTC → JSON. Free-source, 60s cache.

Flatten nested JSON to dot-notation key/value pairs. GET /json-flatten?json=<url-encoded JSON> → flat object. Deterministic, instant.

Mortgage payment and total interest calculator. GET /mortgage?principal=300000&rate=6&years=30 → monthlyPayment, totalPaid, totalInterest. Deterministic JSON, instant.

On-demand web research digest — free-source curated (Wikipedia + Hacker News + Jina Reader). GET /research?q=<topic>; pay per request in USDC on Base. Runs on any install, $0 source cost.

Real-time stock quote (price, currency, previous close, exchange). GET /stock-quote?symbol=AAPL → JSON. Free-source market data.

WHOIS lookup with IANA referral follow. GET /whois?domain=example.com → registrar whois text as JSON. Live registry data.