How MCP Tools Can Replace Manual Hex Pasting in Crypto KAT Debugging

When a Known Answer Test fails on a cryptographic primitive, developers typically diagnose the issue by pasting raw hex and ACVP JSON into a chat prompt, but this approach breaks down with large vector files. For small-scale testing, running the KAT binary locally and copying only the failing vector ID and byte offset into a prompt remains a practical and auditable method. The article proposes exposing KAT runners as Model Context Protocol tools over stdio for cases involving massive ACVP payloads and repeated test cycles. Two key tools are suggested: one to run the crypto KAT and return structured status with a diff window, and another to load ACVP vectors with filtering instead of dumping entire files. The core principle is keeping tool outputs small and typed so the AI agent requests additional context on demand rather than receiving the full file by default.