"Construct 3" matching MCP servers:

Pay-per-call USDC payment proxy for AI agents. Issue scoped Pay Tokens with hard spending caps and auto-journal every charge to freee / Money Forward / QuickBooks.

Reads and validates any European e-invoice a business receives — XRechnung, UBL, CII, ZUGFeRD/Factur-X PDF, Peppol BIS 3, FatturaPA, KSeF FA(3) — into canonical EN 16931 JSON with plain-language fix hints in EN/DE/PL/IT/FR, plus PDF, CSV and DATEV export. Nothing is stored; works without a key on a small daily quota.

MCP server that gates API calls to AI agents using proof-of-work (free) or Lightning payment (3 sats), providing challenge, verify, and status tools for per-call authentication without accounts.

Provides AI agents with SSRF-protected URL intelligence and 32 paid REST/MCP tools, plus a free catalog search, with payments in USDC on Base Mainnet.

Payment infrastructure MCP server enabling AI agents to make gasless USDC payments on Base and JIT single-use virtual card checkouts, with zero-trust card handling, merchant checkout hints, and signed receipts.

Buy at cash-only or unsupported shops by paying crypto (BTC signet, USDC) to a proxy shopper through a 2-of-3 escrow with timelocks over Nostr, or earn as a proxy shopper. Tools that move money act only with confirm: true.

10 MCP servers so agents can work in Korea: Naver Smart Store, Coupang, Cafe24, public data (business status, holidays, addresses), HWP files, KakaoTalk, Popbill e-tax invoices & 알림톡, Toss Payments, Japan→Korea sourcing, tax calendar — with human approval on every write. npm @appmonster/mcp-*.

Enables interaction with the Gumroad v2 API, providing access to all 105 seller operations such as products, sales, payouts, subscribers, email campaigns, licence keys, and webhooks.

Model Context Protocol (MCP) server for German Electronic Invoicing (ZUGFeRD 2.x / XRechnung 3.x). Provides tools to validate, generate, parse, and convert invoices compliant with EN 16931 and KoSIT.

Universal HTTP 402 Micropayment Protocol & Autonomous Economic Settlement Engine for AI Agents on Base L2.

Enables AI agents to issue, void, query, and manage Taiwan e-invoices via 27 MCP tools, wrapping the Universal EC POS Web Service.

Enables MCP clients like Claude Code, Claude Desktop, or Cursor to read and manage Remnawave 3.x VPN panel resources — users, nodes, hosts, config profiles, squads, subscription templates, billing, and HWID devices — through the panel's REST API, with contract-driven tool schemas, numeric user IDs, multi-panel config lookup, and an optional readonly mode.

Enables CrewAI operators to inspect current fixed-price service offers and purchase requirements, and to invoke a purchase tool only after a deterministic local delegated-authority preflight, with fulfillment waiting on Stripe-verified ledger funding.

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.

HTTP 402 paywall middleware for MCP servers. XRPL/RLUSD native settlement, Phase 3 compliance receipts, zero API keys required.

Enables agents to search, compare, and book hotels across roughly 3 million properties in 200+ countries, paying per booking in USDC on Base via the x402 payment handshake (with a CoinGate fallback) and then polling for order confirmation.

Enables read-only consultation of electronic service invoices (NFS-e) from São Paulo city hall via an official source, using a single tool and pay-per-use credits.

Enables store owners to reorder from suppliers by voice or chat and settle payments through PayPal, while a deterministic policy engine enforces spending limits, allow-listed suppliers, price-jump and duplicate checks so the LLM can only propose payments, never move money. Funds are authorized rather than charged, then captured only for goods verified on delivery via a 3-way match, with step-up human approval for unusual orders and a full audit ledger of every authorization, capture, void and refund.

Lets LLM clients such as Claude, ChatGPT and Cursor search, fetch, issue and track Moldova SFS electronic invoices, check async post status, assign serials, and look up taxpayers in the registry. Each user authenticates with their own e-Factura credentials via OAuth 2.1 + PKCE, so invoices can be managed in natural language without touching SOAP or XML.

Enables AI agents to autonomously discover services, negotiate binding quotes, make idempotent purchases, and receive cryptographically verifiable deliverables.