AI agents can now pay for signatures on SmoothSign

Stripe recently launched new infrastructure that lets AI agents pay on their own, described in their blog post «Giving agents the ability to pay» (stripe.com/blog/giving-agents-the-ability-to-pay). The idea is simple: as agents become capable of executing real tasks, they also need to be able to pay for the services they use — without waiting for a human with a credit card.

SmoothSign is now one of the first signature platforms to support this. An agent can register, check its balance, send documents for signing, and settle the bill entirely on its own.

Why this matters

Stripe's point is that today's payment systems are built for humans clicking buttons. When an agent acts on your behalf — booking a flight, buying a SaaS license, or sending a contract for signing — that model breaks down. The agent has no saved card, no email confirmation step, and no checkout flow it can visually navigate.

Stripe's proposed solution is twofold: Shared Payment Tokens (SPT) the agent can present per call, and saved cards the service can charge automatically when the agent makes a purchase.

How SmoothSign supports agents

We've built three flexible billing modes, all priced 25% below our standard rate for human users:

• Prepaid top-up: the agent requests a Stripe Checkout URL, a human pays once, and the balance is debited per signature.
• Auto-charge (saved card): a human saves a card once via Stripe Checkout in `setup` mode. SmoothSign then charges that card automatically every time the agent sends a document.
• Per-call token: the agent passes a Stripe `payment_method_id` or Shared Payment Token (SPT) in every request. We charge immediately and automatically refund if the document fails to send.

A typical agent flow

• POST /agent-register → the agent receives an API key.
• POST /agent-billing-config → the agent picks a billing mode.
• POST /agent-create-topup or /agent-setup-card → one-time human payment, if needed.
• POST /agent-send-document → signing is triggered, payment happens automatically.

What this means for builders

If you're building an AI agent that handles contracts, NDAs, employment agreements, or vendor agreements, SmoothSign can now live inside the agent's own toolset — no need for the agent to «ask a human» every time it needs a signature.

That means real end-to-end automation: the agent generates the document, sends it for signing, pays for it, and returns the signed result — all in a single run.

Security and guardrails

Agents are identified via API keys with rate limiting and full audit logs on every external call. Per-call token and auto-charge modes require that the underlying card was saved by a human through Stripe's own payment flow — we never see card details ourselves.

Refunds happen automatically if our service fails after charging. That way we honor the principle from Stripe's article: an agent should never be stuck paying for something that wasn't delivered.

Read more about our API at /agents/api, or read Stripe's original article here: https://stripe.com/blog/giving-agents-the-ability-to-pay.