loop-mcp

An MCP server providing 15 pay-per-call tools for Bitcoin price data, Lightning address resolution, transaction decoding, and various developer utilities like JSON validation and hash generation, with payments handled via sats over Lightning (L402).

Endpoint and access

No sign-in to connect and list tools. Individual tools may still need a vendor account, credentials, or permissions; check the documented prerequisites.

Vendor evidenceStreamable HTTPNo sign-inEndpoint checked 2026-11-06Operated by Loop XXI LLC

MCP endpoint (Streamable HTTP)

https://mcp.loopxxi.com/mcp

Vendor documentation

What its tools do

16 tools, grouped by the hints the server advertises. Hints are self-declared, not verified behavior.

Read-only (16)

btc_price
btc_send_decision
lightning_address_resolve
tx_decode_explain
optimal_send_window
json_validate
json_extract
csv_to_json
text_analyze
hash_generate
base64_convert
timestamp_convert
uuid_generate
url_parse
jwt_decode
business_ratios

16 of 16 have a description · 16 of 16 declare behavior hints · 15 of 16 with parameters document them all

Checks and signals

Each line is separate evidence, not a trust score.

Passed Endpoint answered the live check · Nov 6, 2026, 2:18 PM UTC
Passed Official MCP Registry namespace is tied to loopxxi.com · Nov 6, 2026, 1:58 PM UTC
Passed Endpoint is on the registry namespace domain · Nov 6, 2026, 1:58 PM UTC
Availability 1 of 1 checks passed in 30 days

What you can do with it

Get BTC price
Resolve Lightning addresses
Decode and explain transactions
Validate JSON and extract data

Source and maintenance

Vendor evidenceRegistry 2.4.0

mcp-registry: com.loopxxi/loop-mcp@2.4.0 Project website

Protocol and capabilities

Server: loop-mcp 2.5.0
MCP protocol negotiated in check: 2024-11-05
Tools: 16 advertised
Resources: Not advertised
Resource templates: Not advertised
Prompts: Not advertised

Server-advertised capabilities

{
  "tools": {}
}

Tools

16 advertised

btc_price

Advertised by the server during the last successful anonymous check.

Advertised read-onlyOpen-world

Get the current Bitcoin price in USD and other major currencies. Source: mempool.space. Real-time. Each reading carries source (the URL read), fetched_at (UTC, RFC 3339) and source_sha256 (SHA-256 of the upstream body as served).

btc_price input schema

{
  "type": "object",
  "required": [],
  "properties": {
    "l402_proof": {
      "type": "string",
      "description": "L402 payment proof \"<macaroon>:<preimage>\". Omit on the first call; an unpaid call returns a 0 sat Lightning invoice and the macaroon. Pay the invoice, then repeat the call with this argument set."
    }
  }
}

btc_price annotations

{
  "title": "Bitcoin Price",
  "readOnlyHint": true,
  "openWorldHint": true,
  "destructiveHint": false
}

btc_send_decision

Advertised by the server during the last successful anonymous check.

Advertised read-onlyOpen-world

Returns a composited send-or-wait recommendation for a Bitcoin transaction. Fetches live mempool and fee data, then outputs a machine-actionable verdict (SEND_NOW, WAIT, or URGENT_ONLY) with fee rates in sat/vB, mempool pressure level, and estimated savings if you wait. Ideal for agents that need a single decision call instead of parsing multiple raw mempool endpoints.

btc_send_decision input schema

{
  "type": "object",
  "required": [],
  "properties": {
    "urgency": {
      "enum": [
        "low",
        "medium",
        "high"
      ],
      "type": "string",
      "description": "How time-sensitive is your transaction? low=economy, medium=default, high=next-block."
    },
    "l402_proof": {
      "type": "string",
      "description": "L402 payment proof \"<macaroon>:<preimage>\". Omit on the first call; an unpaid call returns a 0 sat Lightning invoice and the macaroon. Pay the invoice, then repeat the call with this argument set."
    }
  }
}

btc_send_decision annotations

{
  "title": "Bitcoin Send Decision",
  "readOnlyHint": true,
  "openWorldHint": true,
  "destructiveHint": false
}

lightning_address_resolve

Advertised by the server during the last successful anonymous check.

Advertised read-onlyOpen-world

Resolve a Lightning Address (user@domain.com) to a payable BOLT11 invoice for a given amount. Handles the full LNURL-pay protocol internally. Returns the invoice plus min/max sendable amounts for validation.

lightning_address_resolve input schema

{
  "type": "object",
  "required": [
    "address",
    "amount_sats"
  ],
  "properties": {
    "address": {
      "type": "string",
      "description": "Lightning Address in user@domain.com format."
    },
    "l402_proof": {
      "type": "string",
      "description": "L402 payment proof \"<macaroon>:<preimage>\". Omit on the first call; an unpaid call returns a 0 sat Lightning invoice and the macaroon. Pay the invoice, then repeat the call with this argument set."
    },
    "amount_sats": {
      "type": "integer",
      "maximum": 100000000,
      "minimum": 1,
      "description": "Amount you want to send, in satoshis. At most 100000000 (1 BTC)."
    }
  }
}

lightning_address_resolve annotations

{
  "title": "Lightning Address Resolve",
  "readOnlyHint": true,
  "openWorldHint": true,
  "destructiveHint": false
}

tx_decode_explain

Advertised by the server during the last successful anonymous check.

Advertised read-onlyOpen-world

Fetch a Bitcoin transaction by txid and return a structured, agent-ready summary: type (P2WPKH/P2TR/P2SH/etc.), input/output counts, fees, fee rate in sat/vB, confirmation status, RBF flag, SegWit/Taproot flags, and a one-line agent_summary string ready for LLM context injection. Saves 500-2000 tokens vs parsing raw TX JSON.

tx_decode_explain input schema

{
  "type": "object",
  "required": [
    "txid"
  ],
  "properties": {
    "txid": {
      "type": "string",
      "maxLength": 64,
      "minLength": 64,
      "description": "Bitcoin transaction ID (64 hex characters)."
    },
    "l402_proof": {
      "type": "string",
      "description": "L402 payment proof \"<macaroon>:<preimage>\". Omit on the first call; an unpaid call returns a 0 sat Lightning invoice and the macaroon. Pay the invoice, then repeat the call with this argument set."
    }
  }
}

tx_decode_explain annotations

{
  "title": "Transaction Decode and Explain",
  "readOnlyHint": true,
  "openWorldHint": true,
  "destructiveHint": false
}

optimal_send_window

Advertised by the server during the last successful anonymous check.

Advertised read-onlyOpen-world

Bitcoin transaction timing intelligence. Returns a congestion forecast for the next 1-4h, a recommended UTC send window when fees are projected at/below your target, a fee trajectory (rising/stable/falling) with a calibrated confidence score, next-block minimum fee, confirmation targets for 3/6/144 blocks, and an RBF-viability flag. A synthesis layer above raw fee data — the decision an autonomous payment agent needs before broadcasting. Source: mempool.space.

optimal_send_window input schema

{
  "type": "object",
  "required": [],
  "properties": {
    "l402_proof": {
      "type": "string",
      "description": "L402 payment proof \"<macaroon>:<preimage>\". Omit on the first call; an unpaid call returns a 0 sat Lightning invoice and the macaroon. Pay the invoice, then repeat the call with this argument set."
    },
    "hours_ahead": {
      "type": "integer",
      "maximum": 6,
      "minimum": 1,
      "description": "How far ahead to search for the optimal window (1-6h, default 4)."
    },
    "target_sat_vb": {
      "type": "number",
      "description": "Your fee ceiling in sat/vB. The recommended window targets at-or-below this rate. Omit to get the lowest-projected window."
    }
  }
}

optimal_send_window annotations

{
  "title": "Optimal Send Window",
  "readOnlyHint": true,
  "openWorldHint": true,
  "destructiveHint": false
}

json_validate

Advertised by the server during the last successful anonymous check.

Advertised read-onlyOpen-world

Validate JSON, identify its root type, and return normalized JSON plus a SHA-256 content hash.

json_validate input schema

{
  "type": "object",
  "required": [
    "json"
  ],
  "properties": {
    "json": {
      "type": "string",
      "description": "JSON text to validate, up to 100 KB."
    },
    "l402_proof": {
      "type": "string",
      "description": "L402 payment proof \"<macaroon>:<preimage>\". Omit on the first call; an unpaid call returns a 0 sat Lightning invoice and the macaroon. Pay the invoice, then repeat the call with this argument set."
    }
  }
}

json_validate annotations

{
  "title": "JSON Validate",
  "readOnlyHint": true,
  "openWorldHint": true,
  "destructiveHint": false
}

json_extract

Advertised by the server during the last successful anonymous check.

Advertised read-onlyOpen-world

Extract one value from JSON using a simple dot path with array indexes, for example users[0].email.

json_extract input schema

{
  "type": "object",
  "required": [
    "json",
    "path"
  ],
  "properties": {
    "json": {
      "type": "string",
      "description": "JSON text, up to 100 KB."
    },
    "path": {
      "type": "string",
      "description": "Dot path such as user.profile.name or users[0].email."
    },
    "l402_proof": {
      "type": "string",
      "description": "L402 payment proof \"<macaroon>:<preimage>\". Omit on the first call; an unpaid call returns a 0 sat Lightning invoice and the macaroon. Pay the invoice, then repeat the call with this argument set."
    }
  }
}

json_extract annotations

{
  "title": "JSON Extract",
  "readOnlyHint": true,
  "openWorldHint": true,
  "destructiveHint": false
}

csv_to_json

Advertised by the server during the last successful anonymous check.

Advertised read-onlyOpen-world

Convert CSV, TSV, semicolon, or pipe-delimited text into structured JSON with bounded row output.

csv_to_json input schema

{
  "type": "object",
  "required": [
    "csv"
  ],
  "properties": {
    "csv": {
      "type": "string",
      "description": "Delimited text, up to 100 KB."
    },
    "header": {
      "type": "boolean",
      "description": "Use the first row as object keys. Default true."
    },
    "max_rows": {
      "type": "integer",
      "maximum": 1000,
      "minimum": 1,
      "description": "Maximum data rows to return. Default 100."
    },
    "delimiter": {
      "enum": [
        "comma",
        "tab",
        "semicolon",
        "pipe"
      ],
      "type": "string",
      "description": "Delimiter name. Default comma."
    },
    "l402_proof": {
      "type": "string",
      "description": "L402 payment proof \"<macaroon>:<preimage>\". Omit on the first call; an unpaid call returns a 0 sat Lightning invoice and the macaroon. Pay the invoice, then repeat the call with this argument set."
    }
  }
}

csv_to_json annotations

{
  "title": "CSV to JSON",
  "readOnlyHint": true,
  "openWorldHint": true,
  "destructiveHint": false
}

text_analyze

Advertised by the server during the last successful anonymous check.

Advertised read-onlyOpen-world

Return deterministic text statistics, estimated tokens, reading time, and a SHA-256 content hash.

text_analyze input schema

{
  "type": "object",
  "required": [
    "text"
  ],
  "properties": {
    "text": {
      "type": "string",
      "description": "Text to analyze, up to 100 KB."
    },
    "l402_proof": {
      "type": "string",
      "description": "L402 payment proof \"<macaroon>:<preimage>\". Omit on the first call; an unpaid call returns a 0 sat Lightning invoice and the macaroon. Pay the invoice, then repeat the call with this argument set."
    }
  }
}

text_analyze annotations

{
  "title": "Text Analyze",
  "readOnlyHint": true,
  "openWorldHint": true,
  "destructiveHint": false
}

hash_generate

Advertised by the server during the last successful anonymous check.

Advertised read-onlyOpen-world

Generate a SHA-256 or SHA-512 digest in hexadecimal or Base64 form.

hash_generate input schema

{
  "type": "object",
  "required": [
    "text"
  ],
  "properties": {
    "text": {
      "type": "string",
      "description": "Input text, up to 100 KB."
    },
    "encoding": {
      "enum": [
        "hex",
        "base64"
      ],
      "type": "string",
      "description": "Output encoding. Default hex."
    },
    "algorithm": {
      "enum": [
        "sha256",
        "sha512"
      ],
      "type": "string",
      "description": "Hash algorithm. Default sha256."
    },
    "l402_proof": {
      "type": "string",
      "description": "L402 payment proof \"<macaroon>:<preimage>\". Omit on the first call; an unpaid call returns a 0 sat Lightning invoice and the macaroon. Pay the invoice, then repeat the call with this argument set."
    }
  }
}

hash_generate annotations

{
  "title": "Hash Generate",
  "readOnlyHint": true,
  "openWorldHint": true,
  "destructiveHint": false
}

base64_convert

Advertised by the server during the last successful anonymous check.

Advertised read-onlyOpen-world

Encode UTF-8 text to Base64 or decode Base64 safely, with standard and URL-safe alphabets.

base64_convert input schema

{
  "type": "object",
  "required": [
    "data",
    "action"
  ],
  "properties": {
    "data": {
      "type": "string",
      "description": "Text or Base64 data, up to 100 KB."
    },
    "action": {
      "enum": [
        "encode",
        "decode"
      ],
      "type": "string"
    },
    "url_safe": {
      "type": "boolean",
      "description": "Use the URL-safe alphabet without padding."
    },
    "l402_proof": {
      "type": "string",
      "description": "L402 payment proof \"<macaroon>:<preimage>\". Omit on the first call; an unpaid call returns a 0 sat Lightning invoice and the macaroon. Pay the invoice, then repeat the call with this argument set."
    }
  }
}

base64_convert annotations

{
  "title": "Base64 Convert",
  "readOnlyHint": true,
  "openWorldHint": true,
  "destructiveHint": false
}

timestamp_convert

Advertised by the server during the last successful anonymous check.

Advertised read-onlyOpen-world

Convert Unix seconds, Unix milliseconds, RFC3339, or ISO dates into normalized UTC timestamp forms.

timestamp_convert input schema

{
  "type": "object",
  "required": [
    "value"
  ],
  "properties": {
    "from": {
      "enum": [
        "auto",
        "unix",
        "unix_ms",
        "rfc3339",
        "date"
      ],
      "type": "string",
      "description": "Input format. Default auto."
    },
    "value": {
      "type": "string",
      "description": "Timestamp value."
    },
    "l402_proof": {
      "type": "string",
      "description": "L402 payment proof \"<macaroon>:<preimage>\". Omit on the first call; an unpaid call returns a 0 sat Lightning invoice and the macaroon. Pay the invoice, then repeat the call with this argument set."
    }
  }
}

timestamp_convert annotations

{
  "title": "Timestamp Convert",
  "readOnlyHint": true,
  "openWorldHint": true,
  "destructiveHint": false
}

uuid_generate

Advertised by the server during the last successful anonymous check.

Advertised read-onlyOpen-world

Generate one to one hundred cryptographically random RFC 4122 UUID version 4 identifiers.

uuid_generate input schema

{
  "type": "object",
  "required": [],
  "properties": {
    "count": {
      "type": "integer",
      "maximum": 100,
      "minimum": 1,
      "description": "Number of UUIDs. Default 1."
    },
    "l402_proof": {
      "type": "string",
      "description": "L402 payment proof \"<macaroon>:<preimage>\". Omit on the first call; an unpaid call returns a 0 sat Lightning invoice and the macaroon. Pay the invoice, then repeat the call with this argument set."
    }
  }
}

uuid_generate annotations

{
  "title": "UUID Generate",
  "readOnlyHint": true,
  "openWorldHint": true,
  "destructiveHint": false
}

url_parse

Advertised by the server during the last successful anonymous check.

Advertised read-onlyOpen-world

Parse an HTTP or HTTPS URL into normalized scheme, host, port, path, query, and fragment fields without fetching it.

url_parse input schema

{
  "type": "object",
  "required": [
    "url"
  ],
  "properties": {
    "url": {
      "type": "string",
      "description": "Absolute HTTP or HTTPS URL, up to 4,096 characters."
    },
    "l402_proof": {
      "type": "string",
      "description": "L402 payment proof \"<macaroon>:<preimage>\". Omit on the first call; an unpaid call returns a 0 sat Lightning invoice and the macaroon. Pay the invoice, then repeat the call with this argument set."
    }
  }
}

url_parse annotations

{
  "title": "URL Parse",
  "readOnlyHint": true,
  "openWorldHint": true,
  "destructiveHint": false
}

jwt_decode

Advertised by the server during the last successful anonymous check.

Advertised read-onlyOpen-world

Decode JWT header and payload claims locally without verifying the signature. The response always marks verification as false.

jwt_decode input schema

{
  "type": "object",
  "required": [
    "token"
  ],
  "properties": {
    "token": {
      "type": "string",
      "description": "JWT compact serialization, up to 20 KB."
    },
    "l402_proof": {
      "type": "string",
      "description": "L402 payment proof \"<macaroon>:<preimage>\". Omit on the first call; an unpaid call returns a 0 sat Lightning invoice and the macaroon. Pay the invoice, then repeat the call with this argument set."
    }
  }
}

jwt_decode annotations

{
  "title": "JWT Decode",
  "readOnlyHint": true,
  "openWorldHint": true,
  "destructiveHint": false
}

business_ratios

Advertised by the server during the last successful anonymous check.

Advertised read-onlyOpen-world

Compute cash runway in months, cash buffer days, current ratio, quick ratio, debt to equity, DSO, DIO, DPO and cash conversion cycle from any subset of a business's own cash, monthly flow and balance sheet figures. Arithmetic only, no network. Each value carries its formula and the inputs it used; a value that cannot be computed is null with a reason.

business_ratios input schema

{
  "type": "object",
  "required": [],
  "properties": {
    "cash": {
      "type": "number",
      "description": "Cash on hand. Every figure uses the same currency unit. May be negative."
    },
    "equity": {
      "type": "number",
      "description": "Total equity. May be negative."
    },
    "payables": {
      "type": "number",
      "minimum": 0,
      "description": "Accounts payable."
    },
    "inventory": {
      "type": "number",
      "minimum": 0,
      "description": "Inventory at cost."
    },
    "l402_proof": {
      "type": "string",
      "description": "L402 payment proof \"<macaroon>:<preimage>\". Omit on the first call; an unpaid call returns a 0 sat Lightning invoice and the macaroon. Pay the invoice, then repeat the call with this argument set."
    },
    "annual_cogs": {
      "type": "number",
      "minimum": 0,
      "description": "Cost of goods sold for the last twelve months."
    },
    "receivables": {
      "type": "number",
      "minimum": 0,
      "description": "Accounts receivable."
    },
    "annual_revenue": {
      "type": "number",
      "minimum": 0,
      "description": "Revenue for the last twelve months."
    },
    "current_assets": {
      "type": "number",
      "minimum": 0,
      "description": "Total current assets."
    },
    "monthly_inflows": {
      "type": "number",
      "minimum": 0,
      "description": "Cash received per month."
    },
    "monthly_outflows": {
      "type": "number",
      "minimum": 0,
      "description": "Cash paid out per month."
    },
    "total_liabilities": {
      "type": "number",
      "minimum": 0,
      "description": "Total liabilities."
    },
    "current_liabilities": {
      "type": "number",
      "minimum": 0,
      "description": "Total current liabilities."
    }
  }
}

business_ratios annotations

{
  "title": "Business Ratios",
  "readOnlyHint": true,
  "openWorldHint": true,
  "destructiveHint": false
}

Prompts

Not advertised

No prompt definitions available.

Resources

Not advertised

No resource definitions available.

90-day uptime

A lightweight connection check about every six hours, sampled on hosts with many listings. It shows the server answered, not that its tools work.

Too few checks for a percentage yet (3 of 3 answered).

2026-11-06: 1 of 1 checks answered
2026-11-07: 2 of 2 checks answered

30-day availability

Aggregated from read-only remote checks; this is not a tool-execution or security guarantee.

Successful checks: 1 of 1 (100%)
Average latency: 768 ms
95th percentile latency: 768 ms

Maintenance history

Public check and source-refresh events. Editorial and ownership records remain private.

Nov 6, 2026, 2:18 PM UTC · probe · passed · 768 ms · metadata changed · 16 tool(s)

Connect from your client

Each snippet registers the same endpoint; pick the client you use.

This server is operated by the named third party. Listing and endpoint checks are not an endorsement or a security audit. Review the operator's permissions, terms, and data handling before connecting. How listings are checked and corrected.

Claude Code

Run this once in a terminal. It registers the remote server. Use --scope project to write .mcp.json for the repo.

Claude Code configuration

claude mcp add --transport http loop-mcp https://mcp.loopxxi.com/mcp

Codex

Run this once. Codex stores MCP servers in ~/.codex/config.toml (or .codex/config.toml in a trusted project).

Codex configuration

codex mcp add loop-mcp --url https://mcp.loopxxi.com/mcp

Cursor

Merge this server into .cursor/mcp.json in your project, then enable loop-mcp in your MCP settings.

Cursor configuration

{
  "mcpServers": {
    "loop-mcp": {
      "url": "https://mcp.loopxxi.com/mcp"
    }
  }
}

Cline

Merge this into cline_mcp_settings.json (Cline → MCP Servers → Configure).

Cline configuration

{
  "mcpServers": {
    "loop-mcp": {
      "type": "streamableHttp",
      "url": "https://mcp.loopxxi.com/mcp",
      "disabled": false
    }
  }
}

VS Code

Merge this server into .vscode/mcp.json. Use MCP: List Servers to start loop-mcp and inspect its tools.

VS Code configuration

{
  "servers": {
    "loop-mcp": {
      "type": "http",
      "url": "https://mcp.loopxxi.com/mcp"
    }
  }
}

Gemini CLI

Run this once. It writes .gemini/settings.json in the current project; pass --scope user for ~/.gemini/settings.json.

Gemini CLI configuration

gemini mcp add --transport http loop-mcp https://mcp.loopxxi.com/mcp

Claude Desktop

Open Claude Settings > Connectors > Add custom connector, enter this server URL and enable it for the conversation. This is a manual remote-connector handoff, not a desktop JSON configuration.

Claude Desktop configuration

https://mcp.loopxxi.com/mcp

Windsurf

Merge this into ~/.codeium/windsurf/mcp_config.json, then refresh MCP in Cascade. Windsurf remote servers use serverUrl, not url.

Windsurf configuration

{
  "mcpServers": {
    "loop-mcp": {
      "serverUrl": "https://mcp.loopxxi.com/mcp"
    }
  }
}

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loop-mcp

Endpoint and access

What its tools do

Read-only (16)

Checks and signals

What you can do with it

Source and maintenance

Protocol and capabilities

Tools

Prompts

Resources

90-day uptime

30-day availability

Maintenance history

Connect from your client

Claude Code

Codex

Cursor

Cline

VS Code

Gemini CLI

Claude Desktop

Windsurf

Let your agent find its tools

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