A developer built a guarded MCP server that lets an AI search, quote, and purchase Cloudflare domains — but only after explicit human approval. The post details the safety architecture: separating discovery from action, using a short-lived quote system, rechecking prices before purchase, enforcing a $20 hard limit, representing money as integer cents to avoid floating-point errors, and using MCP elicitation for the approval step. It also covers a concurrency bug fix (consuming single-use state before awaiting async approval) and the policy of never retrying ambiguous billable requests. The resulting toolkit is sold as a $20 one-time purchase on Prototyped.
Table of contents
I split registration and DNS into two toolsI started with the Cloudflare boundaryA purchase starts with one exact domainI represented money as integer centsA quote is a temporary decision recordThe server checks everything againMCP elicitation provides the human approvalI found a concurrency bug before the real purchaseAn ambiguous network result is not retriedI tested the rules before touching a real accountI ran one real purchase lastWhat the prototype includes1.2K Impressions1 Comment