My MCP Server Got Rate-Limited After Auth. Here's the 5-Line Fix.

Short summary

MCP servers face devastating rate-limit burnout after OAuth handshakes—agents silently bypass the spec's auth-only layer and hammer backends until the bill hits $47K+ in hours. The MCP spec settles auth as OAuth 2.1 but omits rate-limiting, and traditional patterns like scopes or API keys fail for headless agents lacking email or payment methods. Captcha-mcp solves this: add PoW or Lightning-based throttling in five lines—agents must either solve CPU puzzles or pay satoshis per call, stopping runaway loops cold.

• •OAuth alone doesn't prevent runaway agents from burning API budgets ($47K in 8 hours reported)
• •MCP spec lacks rate-limiting layer; traditional auth patterns (scopes, keys) don't work for headless agents
• •captcha-mcp adds PoW or Lightning-based throttling in 5 lines of npm/config—agents solve puzzles or pay sats per call

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