Addsign MCP Server

addsign-mcp

MCP server for AddSign — lets AI agents send documents for signature, track signing status, remind signers, and download signed, hash-verifiable PDFs.

Stateless by design: it speaks only AddSign's public v1 API with your API key. No database access, no shared secrets. Revoking the key at addsign.io/settings/api kills the integration instantly.

Setup

1. Create an API key at addsign.io → Settings → API Keys (free on every plan; Free includes 8 documents/month).
2. Set it in the environment — never in prompts or config committed to git:

export ADDSIGN_API_KEY=sk_...

Claude Code

claude mcp add addsign --env ADDSIGN_API_KEY=sk_... -- npx -y addsign-mcp

(Until the npm package is published, point at a checkout instead: claude mcp add addsign --env ADDSIGN_API_KEY=sk_... -- node /path/to/simple-sign/mcp/dist/index.js)

Claude Desktop (claude_desktop_config.json)

{
  "mcpServers": {
    "addsign": {
      "command": "node",
      "args": ["/path/to/simple-sign/mcp/dist/index.js"],
      "env": { "ADDSIGN_API_KEY": "sk_..." }
    }
  }
}

Environment

Tools

No destructive tools: an agent cannot cancel or delete a legal document through this server.

A typical agent flow

list_templates                      → find "Contract to Lease", roles: [tenant_1, tenant_2]
send_for_signature {template_id,
  signers: [Artem…, Valeria…],
  request_id: <uuid>}               → document_id, status: pending, usage 3/8
check_status {document_id}          → Artem signed, Valeria viewed
remind {document_id, valeria@…}     → reminded (or skipped: reminded_recently)
download_signed {document_id}       → url + sha256 → fetch, verify, file it

Error semantics

Every AddSign error carries a stable error_code; this server appends the right next step for the agent. The two that matter most:

• rate_limited (429) — back off retry_after seconds, retry.
• plan_limit_reached (402) — never retry; the monthly cap resets on the 1st or the human upgrades.

Development

cd mcp
npm install
npm run build     # → dist/index.js
ADDSIGN_API_KEY=sk_... node dist/index.js