captcha-mcp

PoW CAPTCHA verification for MCP clients.

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What it can do

  • Challenge: Request a fresh PoW challenge from the PowForge captcha service. Returns {id, salt, difficulty, signature, instructions}. The agent must find a nonce such that SHA-256(salt + nonce) has at
  • Verify: Verify a PoW solution. Input: {salt, nonce, id, signature, algo?, difficulty?} from a prior challenge call plus the nonce the agent computed. Returns a 5-minute HMAC-signed token on success, o
  • Status: Return PowForge captcha server health, lifetime stats (pow_solves, ln_skips, challenges_issued), and L402 endpoint metadata (scope, price_sats, paid endpoint URL). Use this to discover the Lig

What data it sees

Do you need an account

No: the server works without sign-in

PoW CAPTCHA verification for MCP clients. Exposes generate_challenge and verify_solution tools — stateless proof-of-work that agents can embed in auth flows. L402 Lightning skip tier available for trusted clients. No API key required for PoW path.

Server tool list (3)

Raw names from tools/list. Only developers need these.

challengeRequest a fresh PoW challenge from the PowForge captcha service. Returns {id, salt, difficulty, signature, instructions}. The agent must find a nonce such that SHA-256(salt + nonce) has at least `difficulty` leading zero bits, then call the verify tool. Free tier — no payment required.
verifyVerify a PoW solution. Input: {salt, nonce, id, signature, algo?, difficulty?} from a prior challenge call plus the nonce the agent computed. Returns a 5-minute HMAC-signed token on success, or {valid: false, reason} on failure. Tokens can be re-verified server-side via POST /api/token/verify.
statusReturn PowForge captcha server health, lifetime stats (pow_solves, ln_skips, challenges_issued), and L402 endpoint metadata (scope, price_sats, paid endpoint URL). Use this to discover the Lightning skip price before paying, or as a liveness check.