E-Signature Without a Subscription

You have one lease to get signed. Or one NDA, one contractor agreement, one consent form. Every e-signature service answers that with the same thing: pick a monthly plan, make an account, put a card on file. Here is the other way — send one document, pay 1000 sats, and the signed copy comes back to your email.

The one-document problem

E-signature is a subscription business. The pricing pages look reasonable until you read the small print: the cheap plans cap you at a handful of documents a month, and the moment you need a second signer or a second document, you are nudged up a tier. If you only sign a few documents a year, you are paying twelve monthly bills to use the tool twice.

And before any of that, there is the wall everyone in software has learned to expect: create an account, verify an email, add a payment card, agree to terms that let the vendor keep your documents on their servers. For a single signature, that is a lot of yourself to hand over — your identity, your billing details, and a copy of a private contract — just to get one PDF signed.

The occasional signer is the person the subscription model is worst for. A landlord with one lease a season, a freelancer with one client contract, a family handling one consent form — none of them should be renting software by the month. They need to pay for exactly one thing, once.

When you need one thing signed, not a yearly plan

A signature step inside an automated workflow

L402 Authentication Flow

# Send a document for e-signature via L402
# Step 1: Send request (returns 402 + invoice)
curl -X POST https://sats4ai.com/api/l402/e-signature \
  -H "Content-Type: application/json" \
  -d '{
    "document": "data:application/pdf;base64,<...>",
    "signers": [{ "name": "Jane Doe", "email": "jane@example.com" }],
    "customer_email": "you@example.com"
  }'

# Step 2: Pay the 1000-sat Lightning invoice

# Step 3: Resend with payment proof
curl -X POST https://sats4ai.com/api/l402/e-signature \
  -H "Content-Type: application/json" \
  -H "Authorization: L402 <token>:<preimage>" \
  -d '{ "document": "data:application/pdf;base64,<...>",
        "signers": [{ "name": "Jane Doe", "email": "jane@example.com" }],
        "customer_email": "you@example.com" }'

MCP & OpenClaw