@powforge/captcha-mcp
Your MCP server returns 429 when agents pound it. captcha-mcp makes them earn their next call instead. Hand the agent a proof-of-work puzzle (free, ~5s of CPU) or a 3-sat Lightning invoice — both are machine-readable backoff signals an autonomous caller can satisfy without an account, email, or API key.
Three tools over stdio or HTTP. Stdlib only. No signup, free fallback, self-hosted, no revenue share.
Why not 429?
429 Too Many Requests is the wrong shape for the agent era. Three patterns recur across MCP server reports:
- Agent frameworks treat 429 as a connection failure. They retry immediately, often with exponential backoff that is still too aggressive, and amplify the overload that triggered the limit in the first place.
- There is no per-caller signal. A 429 fires for the bucket, not the agent. One noisy caller gets every other caller throttled, and the server has no way to ask the noisy one to slow down specifically.
- Retry-After is advisory and frequently ignored. Agents do not consistently parse it, do not consistently respect it, and have no incentive to wait — the cost of retrying is zero.
