@Loop-XXI
Basic information
L402-native MCP payment proxy: 5 paid Bitcoin/Lightning tools for AI agents, 10-25 sats/call.
Add this server to your MCP-compatible client using the configuration below.
{
"mcpServers": {
"loop-mcp": {
"type": "streamable-http",
"url": "https://mcp.loopxxi.com/mcp"
}
}
}Tool list not available yet
This listing does not currently have a tool list to display. This does not mean the server has no tools; check its documentation for supported capabilities.
Fetch the live tool list directly from this server's endpoint using the button above.
loop-mcp is a payment-aware transport for the Model Context Protocol (MCP) that charges AI agents per tool call over two rails: Bitcoin/Lightning via L402 or USDC via x402, and settles both into one canonical ledger. It is built and maintained by Loop XXI LLC and is API-compatible with x402-only MCP transports, adding Lightning as a first-class second rail. It is intended for developers who want to make MCP tools payable and for agents that need to pay per tool call.
Use the hosted deployment at https://mcp.loopxxi.com/mcp (no install required) — point any MCP/L402 client at it. Alternatively, embed the dual-rail transport into your own MCP server by installing @loop-xxi/loop-mcp from npm and calling makePaymentAwareServerTransport with per-tool USD prices and optional Lightning provider configuration. The agent flow is: challenge (HTTP 402 with invoice) → pay invoice → retry with Authorization: L402 <token>:<preimage>. Fiat credits via Stripe use a single Authorization: Bearer loop_<credit_key> call.
LoopLedger with a rail tag.POST https://mcp.loopxxi.com/try/btc_price returns live Bitcoin price for free.L402 uses Lightning invoices and preimage verification with the `Authorization: L402 <token>:<preimage>` header; x402 uses USDC on Base with an `X-PAYMENT` header. loop-mcp supports both and tags each row in the ledger with the rail used.
For the default Lightning rail, yes — you need a wallet that can pay BOLT11 invoices and return the 64‑character hex preimage. Alternatively, you can buy fiat credit packs via Stripe and pay with a Bearer token, no Lightning wallet needed.
Each tool costs between 10 and 25 satoshis per call, as shown in the tool table (e.g., `btc_price` = 10 sats, `tx_decode_explain` = 25 sats). Fiat credits are priced in sats at the live Bitcoin price ($10 pack gives 1000 credits → sats).
loop-mcp verifies payments statelessly for L402 (no database) and forwards fiat credit debits to Loop Gateway’s `POST /v1/credits/debit`. The ledger is a `LoopLedger` that can be configured by the server operator.
Yes, the endpoint `POST https://mcp.loopxxi.com/try/btc_price` returns the live Bitcoin price for free, without any payment or wallet — it is a read-only lead‑gen endpoint.
Soar Flight Booking MCP is a remote MCP server available at https://mcp.soar.flights.
DeepMark helps teachers deliver rapid, consistent marking with meaningful feedback for every student — in a fraction of the time. What once took a week, now takes one free period.
Connect your AI assistant to your own YOUB endurance training account. Read recorded activities with full analysis, planned sessions, race goals, wellness (HRV, sleep, resting HR) and your athletic profile. Create or mov
AI Agents & MCPs & AI Workflow Automation • (~400 MCP servers for AI agents) • AI Automation / AI Agent with MCPs • AI Workflows & AI Agents • MCPs for AI Agents
YC (S26) | Open Computer History | Continuously record your company computer work, map your workflows, help you find work worth automating, and power your agents' context
Comments