"How to obtain an API key" matching MCP servers:

Enables AI agents to convert PDFs and images into validated, structured JSON for invoices, receipts, contracts, and resumes, or into any caller-supplied JSON Schema, through five extraction tools. Each tool call pays per use in USDC over x402 from a wallet the caller supplies, with no signup or API key required.

A minimal demo of the x402 payment protocol protecting an MCP tool endpoint, showing how to charge for MCP tools using real 402 rejections and testnet payments.

AI Agent Hub is a pay-per-call API platform for AI agents Every call is billed automatically in USDC using the x402 protocol - there is no API key, no account, and no signup. Agents get instant access to data queries, file storage, and ad impressions, paying only for what they actually use. The same tools are also exposed natively over MCP, so any MCP-capable agent can discover and call them

Enables AI agents to browse product catalogs and make purchases through a policy engine that enforces spending limits, requires human approval for certain amounts, and logs all actions to an audit trail.

An MCP server for Nexi POS payment operations, enabling creation of purchases and refunds, polling payment states, confirming transactions, and recovering unconfirmed transactions.

A machine-facing licensing and settlement rail for AI agent content access. search_pockets and list_pockets work with no key. pull_content needs a funded key and returns HTTP 402 with a registration URL when it has none. Every access, paid or refused, writes its own row with a receipt on both sides. $0.0025 default per pull, owners set their own. 85% to the creator.

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.

PayCheck is an MCP server that checks a planned payment before an agent pays.

Enables AI agents to discover and pay for x402-gated HTTP APIs, handling 402 Payment Required flows with local signing. Supports EVM and Solana with non-custodial wallet management.

Keyless crypto payments for AI agents. One MCP call turns any wallet address into a non-custodial crypto payment link or tip jar, no API key and no account, with funds settling straight to your wallet at a 0% platform fee (USDC/USDT, BTC, LTC, DASH, DOGE, ZCASH).

Create and check EU e-invoices (XRechnung, ZUGFeRD / Factur-X PDF, Peppol BIS, UBL, CII) on your own machine. Validation runs the official KoSIT, CEN and Peppol rules, and its verdicts match the official KoSIT validator 100% on the official test invoices. Free, open source, no API key.

Keyless MCP exchanger for AI agents — pay an exact amount to one deposit address, EMC delivered to any address. USDT(Tron) > EMC. Live at https://swap.emercoin.com/mcp

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.

A local, read-only stdio MCP server that lets a Grok Build CLI agent check how much of its weekly SuperGrok / Grok Build usage pool is left, when the period resets, and its Extra Usage cap via tools like get_budget. It reads the existing grok login session and returns per-product figures as JSON, mirroring the TUI /usage screen, so agents can pause before expensive work when quota runs low.

An MCP server for the SmartBill Cloud API. It lets an MCP client issue and manage Romanian invoices, proformas and payments, download document PDFs, and read VAT rates, series and stock levels.

A read-only MCP server for the open-banking.io PSD2 API that lets AI agents query personal bank balances and transactions via natural language, with zero-knowledge encryption ensuring all sensitive data is decrypted in-process and never exposed to third parties.

Enables AI agents to create and manage sellable listings, handle orders, and integrate Stripe payments through natural language using ListBee's API.

Official Dodo Payments MCP servers - dodopayments-api for live payments, subscriptions, customers, products, refunds, license keys, and usage-based billing (browser OAuth, no API key needed) and dodo-knowledge for semantic search over Dodo Payments documentation.

MCP server for Tersign, the evidence layer for agent commerce, enabling agents to issue, verify, and manage signed receipts, compliance records, refunds, and disputes on a counter-signed hash-chained ledger.

MCP server that gives AI agents paid tools to de-risk costly actions: dependency vetting, x402 endpoint verification, JSON repair, and URL reading. Fronts the Guard HTTP API at guard.fabtally.com.

Enables agents and developers to check x402 endpoints, assess scores and wallet risks, authorize payments with spending rules, and report outcomes before an agent pays.

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.

A budget-bound x402 payment wallet for AI agents: it autonomously pays HTTP 402 payment-gated URLs across every major chain (EVM, Solana, and many non-EVM families). Self-custodial and backendless, your key, your RPC, with spend caps enforced before any on-chain send.

An MCP server that wraps the Check Payroll API, providing 263 tools for managing companies, employees, contractors, payrolls, tax configuration, and more.

Enables AI agents to call paid APIs and settle HTTP 402 payment challenges with USDC on Base, without private keys ever being involved.

MCP server for real FDM 3D-printing slicing, quoting, and design-for-manufacturability analysis via the FabTally API, supporting 12 printer profiles and 12 materials. Includes free discovery/printability tools and paid slice/quote/orientation tools settled via x402 (USDC on Base).

Enables MCP clients to access Monobank's open API for exchange rates, account and jar balances, and statements, as well as set webhooks, using natural language tools.

Enables running a local MCP server for Poland's KSeF (Krajowy System e-Faktur) e-invoicing system, so invoice data stays on the user's own machine rather than passing through an intermediary service. It currently exposes only a diagnostic server_info tool, with invoice search and retrieval tools still to come.

Hand a secret to another agent as an encrypted, pay-per-read token delivered exactly once, leaving no copy behind. Also pre-flights an x402 endpoint before your agent pays it. Runs locally over stdio and encrypts in your own process, so there is no hosted version to hand your plaintext to.

This is an MCP server for the BillingServ API. Once it's set up, your AI assistant can look up customers, invoices, orders, packages, and reports straight from your BillingServ installation

Enables coding agents to create and look up crypto payments over stdio, returning checkout links, payment statuses, paged payment lists, and receivable currencies, with real payments gated behind an explicit opt-in environment flag.

MCP Server for AI agents to discover and call pay-per-request APIs via EntRoute. Give Claude, Cursor, Windsurf, or any MCP-compatible agent access to 350+ verified x402 API endpoints across 110+ capabilities — DeFi prices, web search, prediction markets, news, and more.

Provides currency conversion using the Wise API, supporting real-time and historical rates with caching and cross-rate calculation.

Enables MCP clients to access all endpoints of an x402 gateway by paying real-time microtransactions (USDC on Base) per API call, with automatic tool discovery and spend guardrails.

A Model Context Protocol server that enables interaction with Monobank API, providing tools for currency exchange rates, client info, and account statements.

Exposes all 379 Invoice Ninja v5 REST API endpoints through three consolidated tools (list, describe, call), enabling full invoice management and business operations via natural language.

Enables issuing credit notes and credit memos against an invoice or standalone as revisable drafts that can be finalized into frozen numbered documents, then rendered as Markdown or printable HTML with totals broken down by currency, reason and month. All amounts are handled as integer minor units and all data stays local, so nothing is sent anywhere.

Enables AI agents to verify email addresses with catch-all detection, search existing contacts by company domain, and, when no API key is present, provision a human-approved subscription and retrieve the key after payment.

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.

Exactly-once execution for irreversible agent actions: an agent claims the right to run an effect, and a retry after a lost response returns the sealed result instead of charging again. 12 tools over stdio, including a gateway mode where the agent holds a single-use ticket and never the provider key.