Cheap per-call checks an AI agent runs before a costly action: deps-check (CVEs/typosquats before installing), x402-preflight (verify an x402 endpoint before paying it), json-repair (coerce LLM JSON to a schema), url-read (public url to clean Markdown for RAG). Per-call via x402 (USDC on Base) or a prepaid credit key. Also an MCP server.