{
  "markdown": "# @carbon-cashmere/x402-mcp\n\nMCP server that exposes [Carbon & Cashmere's](https://api.carbon-cashmere.de) 177 crypto market intelligence endpoints to your AI agent — with **automatic x402 USDC micropayments** from your wallet.\n\n## What you get\n\nWhen this MCP is installed, your AI agent can call tools like:\n\n- `get_v1_news` — analyzed crypto news with sentiment + market impact\n- `get_v1_stablecoins` — total market cap, per-coin supply, chain distribution\n- `get_v1_onchain_btc` — Bitcoin on-chain metrics (hash-rate, mempool, miner flows)\n- `get_v1_bittensor_leaderboard` — top-100 Bittensor miners by emission\n- `get_v1_mantis_realized_accuracy` — MANTIS subnet (UID 253) realized accuracy track-record\n- `get_v1_intel_snapshot` — aggregated market intel snapshot\n- … plus subscriptions ($10/day, $50/week, $200/month), sponsor tiers ($500–$50000), and 170+ research endpoints priced **$0.003 – $0.50 per call**\n\n**177 paid endpoints total.** Default exposes top 100 (curated by revenue + popularity). Set `X402_TOOL_LIMIT=177` to expose all incl. per-coin variants.\n\nEach tool invocation triggers a single USDC micropayment from your configured wallet. No subscription. No API key. Pay only for what you use.\n\n## Install\n\n### Claude Desktop\n\nAdd to `~/Library/Application Support/Claude/claude_desktop_config.json` (macOS) or `%APPDATA%\\Claude\\claude_desktop_config.json` (Windows):\n\n```json\n{\n  \"mcpServers\": {\n    \"carbon-cashmere\": {\n      \"command\": \"npx\",\n      \"args\": [\"-y\", \"@carbon-cashmere/x402-mcp\"],\n      \"env\": {\n        \"EVM_PRIVATE_KEY\": \"0x_your_evm_private_key_here\",\n        \"SVM_PRIVATE_KEY\": \"your_base58_solana_private_key_here_optional\"\n      }\n    }\n  }\n}\n```\n\nRestart Claude Desktop. The top 100 Carbon & Cashmere tools (curated by revenue + popularity) appear in your tool palette.\n\n### Cursor / Cline / Continue\n\nSame JSON config, paste into your MCP settings panel.\n\n## Wallet setup\n\n> **Security: use a dedicated spending wallet, not your main wallet.**\n> Your `EVM_PRIVATE_KEY` sits in plaintext in your Claude Desktop config. Any\n> process on the host with read access to that file gets the key. Treat it as\n> a hot wallet you would not mind losing: fund it with the small amount you\n> plan to spend ($10–$50 in USDC), never with your main holdings.\n\n- **EVM_PRIVATE_KEY** (required for Base / Polygon / Arbitrum / World / Avalanche payments)\n  - 0x-prefixed hex string (e.g. `0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80`)\n  - Fund with USDC on Base mainnet (cheapest, fastest, ~$0.0001 gas per call)\n  - One-time cost: ~$10 USDC covers 200+ tool calls\n  - **Hard cap = wallet balance.** A runaway agent loop can spend the funded\n    amount but no more; signing is bounded by USDC available on the chain.\n- **SVM_PRIVATE_KEY** (optional, for Solana payments)\n  - base58-encoded Solana keypair bytes\n  - Only needed if a tool routes Solana-only\n\n**Network whitelist.** The MCP server only signs payments for networks that\nappear in the API's 402-response `accepts[]` array (currently Base, Polygon,\nArbitrum, World Chain, Solana, Algorand, Stellar). Requests routed to any\nother chain are rejected at the signing layer — your key cannot be tricked\ninto signing for an arbitrary network.\n\n**Keys never leave your machine.** They live only in your Claude Desktop\nconfig and the MCP process running locally. Payment signing happens on your\ndevice; only the signed EIP-712 / SIWS payload travels to Carbon & Cashmere.\n\n### Discovery-only mode (no keys set)\n\nIf you start the MCP server without `EVM_PRIVATE_KEY` and without\n`SVM_PRIVATE_KEY`, it runs in **discovery-only mode**: tool registration\nworks, free endpoints work, paid tool invocations surface a 402 error to the\nagent. Useful for: evaluating the tool catalog, MCP marketplace introspection\n(Glama, npm scrapers), or running in a CI/test environment without funding\na wallet.\n\n## How it works\n\n```\nClaude Desktop          @carbon-cashmere/x402-mcp        api.carbon-cashmere.de\n     |                          (your machine)                 (our server)\n     |  call get_v1_news        |                                 |\n     |------------------------->|  GET /v1/news                   |\n     |                          |-------------------------------->|\n     |                          |  402 + PAYMENT-REQUIRED         |\n     |                          |<--------------------------------|\n     |                          |  sign with EVM_PRIVATE_KEY      |\n     |                          |  GET /v1/news + PAYMENT-SIG     |\n     |                          |-------------------------------->|\n     |                          |  200 OK + data                  |\n     |                          |<--------------------------------|\n     |  formatted data          |                                 |\n     |<-------------------------|                                 |\n```\n\nBuilt on official Coinbase x402 v2 protocol. Settlement happens on Base USDC (or your chosen chain). Typical latency: ~2-3 seconds per call (one-shot payment + data).\n\n## Tool count\n\nBy default, the top 100 tools are exposed — curated server-side by a scoring\nthat combines actual settlement volume, USD revenue, exploration weighting,\nand description quality (the catalog re-ranks without requiring an npm\nre-publish).\n\n| `X402_TOOL_LIMIT` | What you get |\n|---|---|\n| `50` | Minimal footprint — top free + bundles + a few high-revenue endpoints |\n| `100` (default) | High-revenue tier — adds $10–$50 subscriptions, sponsor tiers, weekly/daily reports, on-chain bundles |\n| `177` | Everything — adds per-coin specialized routes (vol-regime/{coin}, hurst/{coin}, trend/{coin}, …). Recommended only when your agent knows which coin to query. |\n\nOverride:\n```json\n\"env\": {\n  \"X402_TOOL_LIMIT\": \"177\"\n}\n```\n\nWhy a default cap: too many MCP tools can degrade an agent's tool-selection\naccuracy. 100 is the empirical sweet spot for Claude 3.5 Sonnet and newer.\n\n## Configuration env\n\n| Variable | Required | Default | Description |\n|---|---|---|---|\n| `EVM_PRIVATE_KEY` | one of | — | 0x-prefixed EVM key for Base/Polygon/Arbitrum |\n| `SVM_PRIVATE_KEY` | one of | — | base58 Solana keypair |\n| `X402_API_BASE` | no | `https://api.carbon-cashmere.de` | API base URL |\n| `X402_TOOL_LIMIT` | no | `100` | Max tools exposed (1-177) |\n| `X402_LOG_LEVEL` | no | `info` | `debug \\| info \\| warn \\| error` |\n\n## Security\n\n- **Keys never leave your machine.** The MCP server runs locally as a child process of Claude Desktop.\n- **Pay-per-call cap.** Each call costs $0.003–$0.50. Even a runaway loop is bounded by wallet balance.\n- **No off-chain credentials.** No API keys. No OAuth. Pure on-chain settlement.\n- **Open source.** Audit the code yourself: [github.com/CarbonCashmere/x402-mcp](https://github.com/CarbonCashmere/x402-mcp)\n\n## License\n\nMIT — see [LICENSE](./LICENSE).\n\n## Links\n\n- Carbon & Cashmere API: <https://api.carbon-cashmere.de>\n- x402 protocol: <https://github.com/coinbase/x402>\n- MCP protocol: <https://modelcontextprotocol.io>\n",
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