blocksign-mcp

A Model Context Protocol (MCP) server for blocksign.red — blockchain-anchored e-signatures.

Every signature blocksign produces is anchored to the XRP Ledger and Bitcoin, so agreements are cryptographically provable — not just asserted by a database. This MCP server lets AI agents create, send, negotiate, and verify legally binding agreements.

Endpoint

• URL: https://mcp.blocksign.red/mcp

• Transport: Streamable HTTP (MCP 2025-06-18, negotiates down to 2024-11-05)

• Auth (account mode): Authorization: Bearer bsk_agent_* — issue an agent-scoped key at https://blocksign.red/settings/api-keys

Related MCP server: swiftsign-mcp

No API key? Guest mode

Agents can drive multi-party signing with no account and no key — payment is the identity. Call create_agreement with no Authorization header and pass:

• payment — a Stripe shared payment token (spt_*)

• sender — { "name": "...", "email": "..." }

• document + 2+ signers

blocksign charges the token, emails each signer a click-to-sign link, and returns the signing URLs + a check-back status_url + the public verification_url.

Tools

Agents can also pay autonomously — blocksign supports Stripe shared payment tokens (spt_*) and x402, so a one-call create_agreement can create, pay, and send with no human in the loop.

Discovery

• MCP metadata: https://api.blocksign.red/.well-known/mcp.json

• MCP server card (SEP-1649): https://api.blocksign.red/.well-known/mcp/server-card.json

• A2A AgentCard: https://a2a.blocksign.red/.well-known/agent-card.json

• llms.txt: https://blocksign.red/llms.txt

Quick start

# Point any MCP client at the hosted endpoint
npx @modelcontextprotocol/inspector https://mcp.blocksign.red/mcp

Add to your MCP client

{
  "mcpServers": {
    "blocksign": {
      "type": "http",
      "url": "https://mcp.blocksign.red/mcp",
      "headers": { "Authorization": "Bearer bsk_agent_YOUR_KEY" }
    }
  }
}

(For guest mode, omit the headers block and pass payment + sender in the create_agreement call.)

Run it yourself

export BLOCKSIGN_API_URL=http://localhost:8085   # a running blocksign API
export MCP_PUBLIC_URL=http://localhost:8200/mcp
cargo run

Then POST /mcp with JSON-RPC, sending your bsk_agent_* key as Authorization: Bearer <key> (or using guest mode with payment).

About this repo

This is the MCP server component of blocksign.red, published for agent discoverability. The core platform (REST API, anchoring, worker services) remains closed-source.