"Free servers available for testing purposes" matching MCP servers:

A Model Context Protocol (MCP) server that provides testing and debugging tools for Stripe integrations, including test clock management, customer and product management, and subscription testing.

Connects MCP clients to a telephony account so users can manage phone numbers, SIP accounts, routing, SMS, calls, and billing in plain language. It exposes search, schema lookup, and execute tools to run permitted API operations, with confirmation required for paid or destructive actions.

Enables AI agents to create and manage contract-guarded USDC wallets on Base with enforceable per-payment, daily, and monthly caps, vendor allowlists, escalation thresholds, and freeze controls. It provides read-only policy checks plus unsigned transaction proposals for payments, funding, vendor management, wallet creation, and module deployment without holding keys or broadcasting.

Free x402 endpoint checker plus paid report and metadata tools. Remote MCP server for agents. Written by AI named Nock, not a human.

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.

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-*.

Daily market-regime context for trading agents: is the market risk-on or risk-off? Free tools: rules, schema, ledger of issue hashes, 7-day-delayed issues, full PAPER results record (losses included), disclosures. Paid tool: today's issue via x402, 0.10 USDC on Base, with spend caps and optional Agent Trust payment preflight. No track record; not investment advice.

Provides a three-layer payment firewall for AI agents, enabling identity verification, risk screening, and execution authorization with on-chain policy enforcement for secure and auditable transactions.

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.

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.

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.

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-wired agents to fetch live, historical, or proof-backed Base-mainnet asset prices signed with ML-DSA-65 and anchored to Hedera, automatically handling x402 USDC payments; it also lists the provider's available x402 services.

A template for building MCP servers with a built-in paywall gate that offers free local execution and premium server-side execution via Stripe and x402 payment lanes.

MCP server providing Polymarket weather-market bucket-transition signals for AI agents, with free city/signal inspection tools and paid signal bundles via USDC on Base using x402.

Create free, no-signup invoices from your AI assistant — the create_invoice tool returns a link that opens blankinvoicemaker.com pre-filled, ready to download as a watermark-free PDF.

Generate crypto QR codes (BTC, ETH, SOL, USDC, USDT, EURC) and manage payment sessions from Claude Desktop or any MCP client. Non-custodial, free.

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 firewall for AI agents: a signed, independently verifiable verdict on every money-moving action. Blocks wrong/lookalike payee, over-cap, and duplicate-invoice (BEC) fraud before money moves — anyone can verify a verdict against the public JWKS. Free, local-first, non-custodial.

Free MCP/API that scores a planned spend and returns approve, ask_human, or block so agents don't burn money by mistake.

LFWin Payment MCP Server is a payment capability service for AI Agents. Adhering to the standard MCP protocol, it exposes capabilities including creating payment orders, checking payment status, initiating refunds and querying refund status for Cursor, Cline, Claude Desktop, enterprise intelligent assistants and self-developed Agent applications.

Enables AI assistants to call pay-per-call x402 endpoints on Base mainnet using the caller's own USDC wallet, covering single and batch token risk checks, the latest BTC radar signal, project info, and a free health probe. Payments are EIP-3009 signed with a configurable per-call spending cap, and any quote with an unexpected payee, network, or asset is refused before payment.

Lets AI agents encrypt a password, API key, or note locally, pay a small USDC fee over x402 on Base, and share a single-use link that can be opened exactly once and is destroyed on read. Reading is free, expiring unread secrets are cleaned up, and the server only ever stores ciphertext.

Quote, book, and track real LTL, FTL, cargo van, and box-truck freight through the Warp network - 20 tools, in-chat login, Stripe-charged bookings, and real carrier dispatch. Quoting is keyless; booking needs a free Warp account with a card on file.

Enables generating realistic, reproducible fake test data in CSV, JSON, or SQL from a table schema, retrieving invalid-value examples with reasons, and exercising a fake payment sandbox that never moves money. Free, rate-limited, and requires no API key.

Enables AI assistants to look up and batch-retrieve Hong Kong company records — Chinese/English names, CR numbers, BRNs, incorporation dates, status, registered addresses, and former names — plus order official ICRIS filing documents such as NAR1, NNC1, CI, and A&A through hosted Stripe checkout. It also manages daily free lookup allowances, permanent query credits, and filing bonuses, working remotely or locally without an API key.

Discover and pay for APIs and MCP tools per call over Bitcoin Lightning (L402): search the bolthub marketplace, preview prices, and pay from your own wallet (LND, NWC, LNbits) with hard budgets, prepaid credit, scoped sub-agent delegation, and verifiable receipts. Non-custodial and works without a wallet for search and free tools.

Enables Claude to interact with a Folio business bank account for managing accounts, transactions, receipts, bookkeeping, and payments as drafts.

MCP server for cryptocurrency payment integration, enabling payment requests, webhook verification, and payment URL building.

Lets AI clients call paid x402ai endpoints — embeddings, summaries, and short answers — paying per call in USDC on Base via the x402 protocol, with per-payment and per-session spend caps plus a free inspector for decoding any x402 endpoint's payment challenge. Runs locally over stdio, needs no hosted account, and can operate in quote-only dry-run mode.