If you're shipping an MCP server that costs real money per call and don't want to gate it behind OAuth or API keys, this wraps the PowForge captcha service into three tools: challenge, verify, and status. Agents solve a SHA-256 proof-of-work puzzle for free tier access or pay 3 sats over Lightning via L402 for instant tokens. No accounts, no credit cards, no confirmation emails. Runs over stdio by default or HTTP with SSE for browser hosts. The PoW difficulty is tunable and tokens last five minutes. Pair it with your own backend by verifying tokens against the captcha service before fulfilling expensive requests.
claude mcp add --transport stdio zekebuilds-lab-captcha-mcp uvx captcha-mcp