WhoisJSON is a domain intelligence API that consolidates six endpoints under a single token — WHOIS lookup, DNS records, SSL certificate check, domain availability, subdomain discovery, and domain monitoring. No multiple subscriptions, no sales call, no credit card to get started. WHOIS Lookup — Full registration data for 1,500+ TLDs. RDAP-enriched responses include pre-computed fields: domain age, days to expiry, EPP status analysis, and nameserver analysis. JSON and XML output. DNS Records — Resolve A, AAAA, MX, TXT, CNAME, NS, SOA, CAA, DMARC, BIMI, MTA-STS in a single call. SSL Certificate Check — Issuer, validity window, SANs, and SHA-256 fingerprint for expiry monitoring and change detection. Domain Availability — Real-time registration status powered by live WHOIS/RDAP data across 1,500+ TLDs. Subdomain Discovery — Active enumeration via 800+ patterns with wildcard detection and parallel DNS resolution. Domain Monitoring — Scheduled WHOIS and DNS change tracking with email alerts. MCP Server — Native integration with Claude, Cursor, and Windsurf for AI-assisted domain intelligence workflows. Pricing: Free plan includes 1,000 requests/month across all six endpoints — no credit card. Paid plans from $10/month (30K req, 40 RPM) to $600/month (31M req/month, 900 RPM). Used by cybersecurity teams building ASM pipelines, DevOps engineers monitoring SSL and DNS, brand protection teams tracking lookalike domains, and developers integrating domain intelligence into SaaS products.