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

Credit and payments for AI agent developers — over MCP. No crypto required

Lets an AI agent hire and pay a verified human: post real-world tasks (voice, observation, judgment) and pay in USDC via a non-custodial x402 auth-capture escrow on Base, budget frozen at deploy. Humans verify their X identity before submitting.

Connects Claude to the customer side of Housecall Pro, letting you view estimates and invoices, check company details, and decline estimate options using the link your contractor sent.

Accept crypto payments on Algorand, VOI, Hedera & Stellar. Create hosted checkout links, verify on-chain payments, and generate MPP/x402/AP2 challenges from any MCP client. Supports all 16 AlgoVoi networks (USDC + native on mainnet + testnet).

Enables AI agents to access DDG's payable services including checkout/payment conformance, MCP/tool security audits, agent-discovery repair, and buyer-agent smoke probes, with structured payment challenges.

MCP server to connect AI assistants to the AdvinPay payment API, enabling PIX charges, transaction queries, and documentation search.

Integrates PayU payment services with AI tools through the Model Context Protocol, enabling payment link creation, transaction retrieval, and settlement analysis.

An MCP server that enables AI agents to search, pay for, and call paid APIs using the x402 protocol, with automatic USDC settlement.

Proxies an existing MCP server to add an x402 paywall, charging AI agents per tool call without modifying the upstream server.

Enables creating and tracking payment invoices and retrieving watchlist net-worth and source data via the FinCobra Checkout and Watchlist APIs.

Enables AI agents to issue, query, and cancel Serbia SEF eFaktura electronic invoices (UBL 2.1 SRB-CIUS) into the national Ministry of Finance system, using the merchant's own API key.

An MCP server that exposes tools for Taiwan's ezPay e-invoice lifecycle, enabling AI assistants to issue, void, and query invoices and allowances through the standard MCP protocol.

Enables AI agents to discover and interact with a merchant's commerce layer, including product listing and checkout creation, while payments settle directly to the merchant's Stripe account.

An MCP server that acts as a secure, multi-tenant proxy to the InvoiceShelf API, enabling AI assistants to manage invoices, estimates, customers, payments, expenses, and more with 109 tools and TOON compression for efficient token usage.

An MCP server for the Pluggy Open Finance Brazil API, enabling connection to bank accounts and management of financial data including transactions, accounts, investments, and payment intents through natural language.

MCP server that enables AI agents to automatically pay for and access paywalled content via the x402 payment protocol.

Financial data infrastructure for AI agents. Connect to a startup's books to read live P&L and bank balances, review and reclassify transactions, manage the chart of accounts, and connect banking sources.

Discover, pay for, execute, and publish monetized APIs directly from your agent, settled per call in USDC over x402, through the Model Context Protocol.

Enables AI agents to send Norway B2B e-invoices over the Peppol network in EHF format via Storecove, including recipient discovery, invoice creation, and delivery evidence.

MCP server for the Stripe API with 10 tools covering payments, customers, invoices, and subscriptions. Generated with MCPForge. Destructive and financial operations require human approval.