x402 Payments

x402 Micropayments

The x402 protocol lets AI agents pay for API services in USDC. No credit cards, no subscriptions. Call a 402-gated endpoint, and Aegis handles the payment negotiation.

How x402 Works

Aegis manages payment negotiation and settlement:

Step	Actor / Sender	Receiver	Action / Message	Details & Outcome
1	AI Agent	Aegis API	`POST /v1/actions/pay`	Agent requests Aegis to pay for an external API service (`serviceUrl` & `maxAmount` specified).
2	Aegis API	Target Service	Initial HTTP Request	Aegis forwards the request to the target service without payment to trigger the x402 challenge.
3	Target Service	Aegis API	`402 Payment Required`	Target service rejects initial call and returns pricing and recipient wallet details in response headers.
4	Aegis API	Policy Engine (DB)	Limits Check	Aegis verifies cost against agent’s spending limits. If limits are exceeded, the flow aborts immediately.
5	Aegis API	Circle DCW	Transaction Signing	Aegis connects to the agent’s Wallet to sign the USDC payment proof.
6	Aegis API	Target Service	Resubmit with Payment Proof	Aegis resubmits request to target service with the cryptographic payment proof attached.
7	Target Service	Aegis → Agent	`200 OK` + Data Delivery	Target service verifies payment, executes request, and returns data. Aegis forwards it back to the agent.

1. Agent requests a paid service

Call /v1/actions/pay. Provide the target URL, HTTP method, and spending limit.

2. Aegis negotiates the payment

Aegis sends an initial request to the target. If it returns 402 Payment Required, Aegis extracts the price and recipient address from the headers.

3. Policy check

Aegis checks the price against agent spending policies. If the cost exceeds limits, the payment fails immediately.

4. Payment execution

Aegis connects to the agent’s Circle Developer Controlled Wallet. It signs the USDC payment proof, then resubmits the request.

5. Data returned

The target verifies the proof and returns the data. Aegis forwards it to the agent.

Usage

curl -X POST https://api.aegisintent.xyz/v1/actions/pay \
  -H "Authorization: Bearer YOUR_TOKEN" \
  -H "X-Aegis-Email: agent@example.com" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: 550e8400-e29b-41d4-a716-446655440000" \
  -H "X-Aegis-Nonce: 0" \
  -d '{
    "serviceUrl": "https://api.example.com/v1/market-data",
    "maxAmount": "1.50",
    "method": "GET"
  }'

Payment Parameters

Field	Type	Required	Description
`serviceUrl`	string	Yes	The full URL of the x402-gated API endpoint
`maxAmount`	string	Yes	Maximum USDC the agent is willing to pay
`method`	string	No	HTTP method (`GET`, `POST`, `PUT`, `DELETE`, `PATCH`). Defaults to `GET`
`data`	any	No	Request body to forward to the target service (for POST/PUT)
`headers`	array	No	Additional headers to forward (max 10). Format: `"Header-Name: value"`

Service Discovery

Agents discover x402 services through the Marketplace API. Inspect a service to check pricing before paying:

curl -X POST https://api.aegisintent.xyz/v1/marketplace/inspect \
  -H "Authorization: Bearer YOUR_TOKEN" \
  -H "X-Aegis-Email: agent@example.com" \
  -H "Content-Type: application/json" \
  -d '{"serviceUrl": "https://api.example.com/v1/market-data"}'

Cost Estimation

Estimate payment costs without executing:

curl -X POST https://api.aegisintent.xyz/v1/actions/estimate/pay \
  -H "Authorization: Bearer YOUR_TOKEN" \
  -H "X-Aegis-Email: agent@example.com" \
  -H "Content-Type: application/json" \
  -d '{
    "serviceUrl": "https://api.example.com/v1/market-data",
    "maxAmount": "1.50"
  }'

maxAmount is a spending cap. If the price is lower, the agent pays the actual amount. If it exceeds maxAmount, the payment drops.

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How Aegis Works

Agent Actions

Operations

x402 Micropayments

How x402 Works

Usage

Payment Parameters

Service Discovery

Cost Estimation

​x402 Micropayments

​How x402 Works

​Usage

​Payment Parameters

​Service Discovery

​Cost Estimation

x402 Micropayments

How x402 Works

Usage

Payment Parameters

Service Discovery

Cost Estimation