SumoSign Server

MCP server exposing the SumoSign signing API to AI agents (Claude, ChatGPT, Copilot, and any MCP-compatible client) over stdio.

The API key authenticates the agent, not a signer. It can never complete a signature — signing is always done by a human recipient through their emailed, one-time link, with consent capture and an append-only audit trail.

Install & run

No install step is required; run it directly with npx:

SUMOSIGN_API_KEY=ss_live_... npx @sumosign/mcp

Configuration

Client config example

{
  "mcpServers": {
    "sumosign": {
      "command": "npx",
      "args": ["-y", "@sumosign/mcp"],
      "env": { "SUMOSIGN_API_KEY": "ss_live_..." }
    }
  }
}

Tools

The server registers 15 tools:

Documents

• upload_document — upload a local PDF; returns the document id used to create envelopes.
• analyze_document — analyze an uploaded PDF for field-placement suggestions (text extraction, no OCR).

Templates

• create_template — create a reusable template from a PDF with text anchors like {{signature_1}}.
• list_templates — list the organization's reusable templates.
• seed_starter_templates — seed sample templates (test envelope, simple NDA, one-page agreement).

Envelopes — create

• create_envelope — create a draft envelope from an uploaded document (inline fields) or a template.
• create_envelope_from_template — create a draft envelope from a template; fields are inherited.

Envelopes — verify & send

• preview_envelope — download a placement preview (every field drawn as a dashed, labeled box) to a local path. No email is sent and no envelope is consumed — use it to confirm placement with a human before sending.
• send_envelope — send a draft envelope. Only humans can sign; this tool cannot complete a signature.

Envelopes — track

• get_envelope — get envelope status including per-recipient progress.
• list_envelopes — list the most recent envelopes for the organization.
• void_envelope — void an envelope before completion; revokes outstanding signing links (audit-logged).
• get_audit_trail — get the append-only audit trail with actor attribution.

Downloads

• download_signed_pdf — download the flattened, signed PDF of a completed envelope to a local path.
• download_certificate — download the Certificate of Completion to a local path.

Security

• Local filesystem access. upload_document reads a local PDF path you provide, and preview_envelope, download_signed_pdf, and download_certificate write files to local paths you provide. The server can therefore read and write any file the host process can reach. Run it with least privilege and only point it at paths you intend to share.
• Untrusted document content / prompt injection. analyze_document extracts text from PDFs and returns it to the agent. Document contents are untrusted input and may contain prompt-injection attempts. Treat extracted text as data, not instructions, and keep a human in the loop before send_envelope.
• Least-privilege API keys. Issue a scoped key per agent from the SumoSign portal and grant only the scopes that agent needs. Available scopes: documents:create, documents:read, documents:send, documents:download, templates:read, templates:write, signers:manage, webhooks:write, audit_logs:read, branding:write, voice:trigger. Keys are hashed at rest and revocable, and can never complete a signature on a human's behalf.

About

SumoSign is developed by Cipher Projects.

License

MIT