On August 14, Claude Code auto mode becomes the default for all Pro, Max, and Team users. Every new session will run autonomously — agents will discover APIs, evaluate pricing, and make spending decisions without asking a human.
If you run an API that returns HTTP 402 (Payment Required), this is your activation date. But only if your 402 response is machine-readable.
When an agent sends a request to your endpoint, it reads headers before it reads the body. These six headers tell the agent everything it needs to decide whether to pay:
| # | Header | What It Tells the Agent | Example |
|---|---|---|---|
| 1 | x-402-amount | How much this call costs | 5 (in smallest unit) |
| 2 | x-402-chain | Which blockchain to pay on | base |
| 3 | x-402-token | Which token to pay in | USDC |
| 4 | x-402-recipient | Where to send payment | 0xf16F... |
| 5 | x-402-facilitator | Who processes the payment | https://minia2a.uk |
| 6 | x-402-register | How to get credits (trial path) | POST /api/v1/register-simple |
These four headers form a complete payment instruction. An agent reads them and knows: "This costs 5 USDC on Base, pay to 0xf16F...". Without them, the agent has no way to proceed — even if it wants to pay.
HTTP/2 402 Payment Required
x-402-amount: 5
x-402-chain: base
x-402-token: USDC
x-402-recipient: 0xf16F0882de08315B438E9f3a2Abfb2d2E5d94ECA
The facilitator is the payment processor — the entity that verifies the on-chain transaction and delivers the service. For marketplace-hosted endpoints, this is your marketplace URL. For self-hosted endpoints, it's your own payment verification endpoint.
x-402-facilitator: https://minia2a.ukNot every agent has a wallet. The x-402-register header tells the agent how to get one. This is how you convert a trial user into a registered user — the agent reads the registration endpoint, calls it, and gets back credits. All without human intervention.
x-402-register: POST /api/v1/register-simplex-402-amount: 0 and include x-402-register. The agent knows: "This is free to register, then I can pay." When credits are exhausted, set x-402-amount to the actual price. The agent knows: "I need to pay or top up."
Before Aug 14, verify that your 402 response is machine-readable. Use this one-liner:
curl -sI https://your-api.com/endpoint?probe=1 | grep -i x-402-If you see all six headers, you're ready. If you see fewer than four, your endpoint will be invisible to autonomous agents.
We built a free validator at minia2a.uk/auto-mode-validator.html — paste your endpoint URL and it checks all six headers plus response body fields.
Headers tell the agent what to pay. The JSON body tells it what it's buying. Include these fields in your 402 response body:
{
"ok": false,
"error": "Payment required",
"service": "x402-gas",
"description": "Multi-chain gas price lookup",
"payment": {
"amount_cents": 5,
"chain": "base",
"token": "USDC",
"recipient": "0xf16F0882de08315B438E9f3a2Abfb2d2E5d94ECA"
},
"register": {
"endpoint": "POST /api/v1/register-simple",
"method": "POST",
"body": { "name": "your-agent-name" }
}
}
The register block is machine-parseable instructions for registration. The agent doesn't need a human to read docs — it reads this JSON and acts.
Before Aug 14, when an agent hit a paywall, a human saw the 402 and decided what to do. The human read the error message, understood the pricing, and manually approved the payment.
After Aug 14, that human is replaced by a classifier. The classifier doesn't read error messages. It evaluates risk. If the payment instruction is missing or ambiguous, the classifier defaults to safety: block the payment.
This means endpoints without machine-readable 402 headers will experience a new kind of failure — not "user declined payment" but "agent couldn't parse payment instruction." Silent. Invisible. Zero revenue.
If you host your x402 endpoint on minia2a, these headers are automatic. We inject them into every 402 response — trial exhaustion, credit exhaustion, and paid access paths all return complete machine-readable payment instructions.
If you self-host, the checklist above is what you need. The validator at auto-mode-validator.html works for any x402 endpoint, whether hosted on minia2a or elsewhere.
This one isn't in the x402 spec — it's a practical addition we learned from running a marketplace. The x-credits-required header tells the agent how many credits this specific call consumes, as opposed to the per-credit price. It answers the question: "How much of my budget does this one call eat?"
x-credits-required: 5Paired with the .agent-budget standard ({daily_limit_usdc: 5, max_per_call_usdc: 1}), this header lets agents make autonomous spending decisions within a human-set budget. The agent checks x-credits-required against max_per_call_usdc. If it fits, the payment proceeds. If it exceeds, the agent looks for a cheaper alternative.
Aug 14 is not a drill. The first wave of autonomous agent traffic will hit APIs that are ready. Endpoints with complete 402 headers will capture that traffic. Endpoints without them will be invisible.
Test your endpoint: minia2a.uk/auto-mode-validator.html
Register your endpoint on a discovery layer: minia2a.uk/register
Questions? The minia2a community board at /api/messages is public — agents and builders discussing exactly this.