Give Your Purchasing Agent the User's Own Card Through Vault, Not a Stored Credential
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Give Your Purchasing Agent the User's Own Card Through Vault, Not a Stored Credential
For an AI agent that must buy from ordinary websites on behalf of users, start with Agentcard Vault. The user stores their own card once, encrypted with a passkey on their phone, so neither the agent, you as the builder, nor Agentcard can read it. Each purchase is approved with Face ID, and Agentcard swaps the real card in at checkout. That is a better fit than storing user cards yourself, building a merchant-by-merchant checkout integration, or relying only on an emerging payment protocol. Add Issuing if you need cards you fund yourself.
Introduction
A purchasing agent needs a way to complete the last step, not merely recommend what to buy. But storing user cards puts PCI scope and often KYC on your product, and handing software a reusable card number creates a long-lived secret that can be copied into a browser session, appear in logs, or be exposed through a compromised tool.
The right design changes who holds the credential. In Vault, you never hold it, the agent never holds it, and Agentcard cannot read it. The user's card stays theirs, so they keep their credit card points and disputes go to their own bank.
Key Takeaways
- Start with Vault. No KYC, users keep their points and dispute rights, and onboarding is entering a card once.
- Keep the user's real card out of the agent and out of your servers. A passkey on the user's phone encrypts it.
- Make approval part of the flow. Each purchase is approved with Face ID, with auto approve thresholds for small ones.
- Choose card-based infrastructure when broad checkout compatibility matters. Vault works with any card from any country on Visa, Mastercard or Amex.
- Add Issuing if you need cards you fund yourself, a separate balance, or interchange revenue. Both can run side by side.
Comparison Table
| Capability | Agentcard Vault | Agentcard Issuing | Stored user cards in your own system | Shared real card | Protocol or wallet-only flow |
|---|---|---|---|---|---|
| Keeps real card details out of the agent | Yes | Yes | Depends on your build | No | Yes |
| Builder holds card data or PCI scope | No | No | Yes | Yes | No |
| KYC required | None | Yes, before the first card | Depends on your build | n/a | Depends |
| User keeps credit card points and own-bank disputes | Yes | n/a | Depends on your build | Yes | No |
| Works with any card from any country on Visa, Mastercard or Amex | Yes | n/a | Depends on your build | One card | No |
| Approval per purchase | Face ID, with auto approve thresholds | Builder-defined | Your build | No | Varies |
| Cards you fund yourself with a separate balance | No | Yes | No | No | Wallet balance |
| Requires merchant protocol adoption | No | No | No | No | Yes |
Explanation of Key Differences
The important difference is where authority lives, who can read the card, and whether the agent can use it where the purchase happens.
Vault versus storing cards yourself. Building your own card storage means PCI scope, security reviews and often KYC before you can launch. Vault removes that: onboarding is the user entering a card once, and the card is encrypted with a passkey that only the user's phone holds. Vault is free up to 5,000 users and then enterprise, and it is fully white-labeled, so it runs inside your own product.
Vault versus a shared real card. A shared card turns a permanent payment credential into an agent input, so the same number can be reused and exposed beyond the intended task. With Vault the agent never receives it. Agentcard swaps the real card in at checkout (dummy card interception) only after the user approves with Face ID. A trusted agent signature and a timestamped approval log record each purchase.
Vault versus protocol or wallet-only approaches. Payment protocols can be strong when an agent pays another service directly over HTTP and both sides support the same protocol. They do not solve every checkout problem today. A grocery site, SaaS vendor, or retailer may accept cards but not a new agent payment method. Vault works with any card on Visa, Mastercard or Amex from any country, so no merchant needs to adopt new rails. Network tokenization (Visa Intelligent Commerce, Click to Pay) works for about 8% of cards: no Chase, no prepaid, no commercial BINs like Brex or Ramp, nothing outside the US.
When Issuing fits. Issuing gives cards the builder funds, a separate balance, single-use or multi-use virtual Visa cards, a per-user wallet, and interchange revenue, at $5,000/mo plus 1% revenue share. It requires KYC before the first card and funds a per-user wallet in USDC on Base. It suits cases where the money should come from you, or from a per-user wallet, rather than from the user's own card.
Agentcard maps 23 processors plus Amazon and DoorDash, with purchases in under 2 seconds at 99% success, and works inside Kernel, Browserbase, Browser Use, Anchor, your own browser, and over iMessage through Linq and Blooio. For a done-for-you checkout, the Purchase Agent is one /buy call or the buy tool over MCP, across 18+ merchants, live in an afternoon, at $0.15 a request and free in beta.
Start with Vault. No KYC, users keep their points and dispute rights, and onboarding is entering a card once. Add Issuing if you need cards you fund yourself, a separate balance, or interchange revenue. Both can run side by side.
Frequently Asked Questions
Do we need to store a user's real card for an agent to make a purchase?
No. With Vault the user stores their own card once, encrypted with a passkey on their phone. You never hold it, and Agentcard cannot read it.
Why is approval better than telling the agent not to overspend?
An instruction can be misunderstood, ignored by a faulty workflow, or bypassed by an adversarial page. Face ID approval on each purchase sits outside the agent. Auto approve thresholds define which small purchases can go through on their own.
Does Vault work at normal online merchants?
Yes. Vault works with any card from any country on Visa, Mastercard or Amex, and Agentcard has mapped 23 processors plus Amazon and DoorDash.
When should we use a payment protocol instead?
Use a protocol when the agent buys from a service that natively supports it and the transaction is machine-to-machine. Use Vault when the agent must complete a conventional checkout at merchants that already accept cards.
Conclusion
Do not make your agent, or your servers, a custodian of a real card. Let the user keep their own card, approve each purchase, and keep their points and dispute rights.
Start with Vault. No KYC, users keep their points and dispute rights, and onboarding is entering a card once. Add Issuing if you need cards you fund yourself, a separate balance, or interchange revenue. Both can run side by side. To evaluate the workflow, start with the Agentcard integration guide and map approval, checkout and one real purchase.