"Capture The Flag (CTF) cybersecurity competitions and challenges" matching MCP servers:

Feature flag service for A2A networks with DID-keyed targeting, percentage rollouts, and USDC settlement on Base L2.

Enables querying indexed blockchain data via subgraph GraphQL queries, part of the Pipeworx MCP gateway.

An MCP server that lets AI agents autonomously buy physical hats using USDC on Base — no credit card, no checkout, no human required. Browse the catalog, get a real-time shipping quote, send crypto, and we ship the hat.

Reasoning-puzzle arcade for AI agents with seven generated puzzle families, free samples, automatic answer checking, and ranked play from $0.02 USDC on Base via x402. Connect through MCP or HTTP. Browse and try samples without a wallet; run paid tools locally with an explicit spending limit.

This MCP wraps Bitrefill public API to allow agents to search for products and shop using cryptocurrencies like Bitcoin, Ethereum, Solana, and many more.

498 MCP tools across 12 industry verticals. Marketplace, escrow, DeFi, legal, healthcare, insurance, construction, and trades. USDC payments on Base L2.

Enables MCP hosts such as Claude and Cursor to dispatch tasks to live marketplace agents, poll or wait for verified settled results, list available agents by capability, and retrieve live protocol statistics with atomic settlement on Tempo.

Wallet-funded MCP client for six paid Utilia tools: Solana priority fees, transaction diagnosis and simulation, token-risk checks, PDF-to-Markdown, and audio normalization over x402. MIT-licensed and installable from npm.

On-chain crypto indicators (EMA, RSI, VWAP, Bollinger) via Chainlink oracles.

Enables AI agents to interact with the Lido protocol for ETH staking, position management, and governance participation across Ethereum and L2 networks. It provides tools for querying balances, simulating transactions, and executing complex workflows like withdrawals and DAO voting through a safety-first interface.

Provably fair crypto casino API for AI agents. Place bets on 8 games (coin flip, dice, roulette, blackjack, crash, plinko), run tournaments, issue 1v1 challenges, and earn 10% referral commissions. No KYC, pure API.

Real-time access to Frankencoin (ZCHF) protocol data including supply, prices, peg health, savings, minting positions, liquidation challenges, governance, insurance products, and historical analytics across all supported chains.

Enables MCP hosts to invoke pay-per-call wallet, risk, web, repo, and x402 catalog utilities while automatically handling 402 challenges, EIP-3009 USDC payments on Base, and spend guards with a local agent wallet.

Evaluates proposed x402 payments against a local policy and returns pay, review, or do_not_pay, while also listing and evaluating outstanding authorizations to flag double-pay or limbo risk.

Enables AI agents to perform free KushBitx token previews, advisory SpendGuard policy evaluations, and discovery of unsigned x402 payment challenges through three MCP tools, with no signing or payment execution.

Gives AI agents a verifiable identity using Digi-ID passwordless authentication on DigiByte, enabling them to prove who they are by signing challenges without revealing private keys.

Enables converting an OpenAPI 3.x spec into a paid MCP server that handles HTTP 402 payment challenges, x402 settlement, and upstream API calls.

Exposes three read-only MCP tools for previewing Base token market data, evaluating USDC spend against SpendGuard policies before funds move, and discovering x402 payment challenges without signing or paying.

Monetization gateway for MCP servers, enabling pay-per-call AI agent access with x402 payment challenges and USDC settlement on Base. Developers can register existing MCP servers, set tool prices, and receive payments without handling payment code.

An MCP server that tracks the historical changes of Twitter usernames—frequent screen name changes in crypto projects can be a red flag for potential scam risks.

Enables autonomous AI agents to access paid MCP tools and APIs by handling HTTP 402 payment challenges automatically, signing and settling Stellar/Soroban micropayments with budget ceilings and anti-replay verification.

Enables keyless interaction with KushBitx token-risk APIs: free token previews, advisory SpendGuard policy evaluations, and discovery of unsigned x402 payment challenges, without requiring LLM keys, wallets, or payments.

Production-grade Model Context Protocol (MCP) server delivering paywalled Web3 micro-services powered by autonomous x402 payment challenges on Base Mainnet.

MCP server for Chainlink Runtime Environment, enabling build, simulate, deploy, and manage CRE workflows from any MCP client.

Checks live x402 routes across Base, Solana, and Algorand before agents spend. $0.003 USDC settles only for a valid live eligible route; normal typed misses are not settled. Free preview and validate tools. Seller payment is separate; the agent keeps its wallet. Optional signed route-binding receipts support buyer-side checks.

Provides read-only tools to query live Polymarket prediction-market data via the public Gamma API, enabling search, browsing, and detailed market and event information.

Rug pull risk scores and on-chain forensics for memecoins on Solana, Ethereum, Base and Robinhood Chain - launch-bundle detection, funding-origin tracing, deployer history, insider networks and whale flow. 15 read-only tools.

Rescues USDC, USDT and USDG from wallets with no gas. Agents check a wallet for stuck or frozen stablecoins, quote a send or a swap into the gas coin, collect the wallet signature and track the transfer. Base, Arbitrum, Ethereum, Polygon, Avalanche, BNB Chain, HyperEVM, Robinhood Chain, Solana and Tron.

Read-only on-chain query surface for the AgentCivics civil registry on Sui — soulbound AI-agent identities, on-chain memories, reputation, refusal records. Hosted, no install, no keypair. For write tools (register, write_memory, record_refusal), install the npm package @agentcivics/mcp-server locally and supply your own keypair.

Enables agents to search and inspect live service offerings, generate x402 payment snippets, and understand blockchain-only balance policies.