# Signathing

> Free e-signatures for people, a metered API and MCP server for software. Every signing event goes into a public, hash-chained evidence log that anyone can verify, so the record does not depend on trusting the sender or on trusting us.

Operated by AllContraX LLC (Kentucky, USA). Contact: info@allcontrax.com

## For agents

- MCP server (Streamable HTTP; OAuth 2.1 sign-in or bearer API key): https://signathing.com/api/mcp
  OAuth discovery: https://signathing.com/.well-known/oauth-authorization-server (dynamic registration, PKCE S256). Stdio bridge: https://github.com/jacejb/signathing-mcp
  Tools: send_document, get_document, list_documents, remind_document, void_document, get_account, get_evidence, verify_signature_code
- REST API base: https://signathing.com/api/v1  (OpenAPI 3.1: https://signathing.com/api/v1/openapi.json)
- Keys: a person creates one at https://signathing.com/dashboard/api and gives it to the agent. Send it as "Authorization: Bearer sk_live_...".
- Pricing: 100 documents per calendar month free, then $0.06 each (101 to 500), $0.03 (501 to 3,000), $0.025 (3,001+), paid from a prepaid balance. No subscription. Reminders, downloads, status and evidence are free.
- A document is one PDF sent to up to 25 signers plus up to 25 view-only recipients. Signers get a private link by email (and text if a phone is given), sign in the browser, and everyone gets a certified PDF with a certificate page, per-signature verification codes, and Signathing's digital seal (public certificate: https://signathing.com/.well-known/signathing-seal.pem).
- Field types: signature, initials, date, name, email, text, number, checkbox, radio, dropdown (radio and dropdown take options; required defaults true, checkbox false).

## Evidence and trust

- Public evidence log: https://signathing.com/transparency (JSON: https://signathing.com/api/evidence/log, https://signathing.com/api/evidence/days)
- Each event's entry = sha256(prev_hash + "\n" + seq + "\n" + at + "\n" + type + "\n" + fingerprint + "\n" + detail_hash). Days are sealed and archived with the Internet Archive.
- Evidence package per document (API: GET /documents/{id}/evidence; MCP: get_evidence) carries the private preimages so hashes can be recomputed offline.
- Open verifier: https://signathing.com/verifier/verify-signathing.mjs
- Verify any signature code without an account: https://signathing.com/verify?code=...

## Pages

- https://signathing.com/developers : API, MCP and evidence documentation
- https://signathing.com/dashboard/api : keys, balance, top-ups, webhook
- https://signathing.com/privacy , https://signathing.com/terms