Standalone Docker

By the end of this guide you will have a running Key0 Docker container that:

Accepts USDC payments from AI agents
Either calls your ISSUE_TOKEN_API to fetch credentials (subscription plans), or proxies to your backend and returns data directly (pay-per-call routes)
Automatically refunds agents if your token endpoint fails or the backend returns an error
Exposes GET /discover, POST /x402/access, and the generated buyer-onboarding bundle

New to Key0? Read Core Concepts first to understand terms like Plan, Challenge, AccessGrant, and EIP-3009. See Two Modes to understand how Standalone differs from Embedded.

Run Key0 as a standalone service in Docker. It handles agent discovery, payment verification, and credential issuance — your existing API only needs to expose a single token-issuing endpoint. By default, standalone also generates buyer-facing onboarding endpoints from your config:

GET /.well-known/agent.json when A2A is enabled
GET /.well-known/mcp.json and POST /mcp when MCP is enabled
GET /llms.txt
GET /skills.md

To distribute a CLI binary to your users: install the SDK, call buildCli(), and upload the output to your preferred host. See the Agent CLI guide for step-by-step instructions.

Setup UI
Environment Variables

Option A: Setup UI (zero-config start)

Start the container with no configuration. The Setup UI walks you through everything visually.

Start the container

The full profile starts Key0 with managed Redis and Postgres — batteries included.Download the Docker Compose file:

curl -fsSL -o docker-compose.yml https://raw.githubusercontent.com/key0ai/key0/refs/heads/main/docker/docker-compose.yml

Then start the services:

docker compose --profile full up

Open the Setup UI

Navigate to http://localhost:3000. On first launch, you are redirected to /setup.The Setup UI lets you configure:

Wallet address — the USDC-receiving address on Base
Network — mainnet or Base Sepolia testnet
Pricing plans — plan IDs, amounts, and descriptions
Token issuance API — the URL Key0 calls after payment to fetch credentials
Settlement and refund settings

Submit and go

When you submit the form, the server writes the configuration and restarts automatically. Configuration is persisted in a Docker volume (key0-config), so it survives container restarts.

Docker Compose profiles

Choose a profile based on what managed infrastructure you need:

Profile	What starts
(none)	Key0 only — bring your own Redis + Postgres via env vars
`--profile redis`	Key0 + managed Redis
`--profile postgres`	Key0 + managed Postgres (still needs Redis externally)
`--profile full`	Key0 + managed Redis + managed Postgres (batteries included)

Managed infrastructure is auto-detected at startup. No connection strings to configure when using profiles.

Option B: Environment variables

Pass configuration directly for scripted or CI/CD deployments.

Set the two required variables

Key0 needs two things to start:

KEY0_WALLET_ADDRESS — your USDC-receiving wallet address (0x…)
ISSUE_TOKEN_API — the URL that Key0 POSTs to after payment is verified

docker run \
  -e KEY0_WALLET_ADDRESS=0xYourWallet \
  -e ISSUE_TOKEN_API=https://api.example.com/issue-token \
  -p 3000:3000 \
  key0ai/key0:latest

Or use Docker Compose

For production, Docker Compose manages Redis alongside Key0:

cp docker/.env.example docker/.env

Edit docker/.env and set KEY0_WALLET_ADDRESS and ISSUE_TOKEN_API, then start:

docker compose -f docker/docker-compose.yml --profile redis up

Even with environment variables pre-configured, the Setup UI is always available at /setup for reconfiguration.

ISSUE_TOKEN_API contract

After Key0 verifies an on-chain USDC payment, it POSTs to your ISSUE_TOKEN_API endpoint with the payment details:

Request body

{
  "requestId": "uuid",
  "challengeId": "uuid",
  "resourceId": "photo-42",
  "planId": "basic",
  "txHash": "0x...",
  "unitAmount": "$0.10"
}

Your endpoint returns any credential shape you need. Key0 forwards the response directly to the agent.

{
  "token": "eyJ...",
  "expiresAt": "2025-01-01T00:00:00Z",
  "tokenType": "Bearer"
}

If your ISSUE_TOKEN_API endpoint returns an error or is unreachable, Key0 automatically initiates an on-chain refund to the paying agent. See Automatic Refunds for details.

Pay-Per-Call Routes (PROXY_TO_BASE_URL)

For top-level routes, Key0 settles the payment and then proxies the request to your backend — no ISSUE_TOKEN_API call is made for these route purchases. The agent receives a ResourceResponse containing the backend’s actual response data.

┌──────────────┐     ┌──────────────────────┐     ┌──────────────────┐
│ Client Agent │     │    key0 (Docker)      │     │  Your Backend    │
│              │────▶│  GET /api/...         │     │                  │
│              │◀────│  402 + requirements   │     │                  │
│              │     │  402 + requirements   │     │                  │
│              │     │                       │     │                  │
│              │     │  verify on-chain      │     │                  │
│              │────▶│  GET /api/... +       │     │                  │
│              │     │  PAYMENT-SIGNATURE    │     │                  │
│              │     │  proxy request ───────│────▶│  GET /api/...    │
│              │◀────│  ResourceResponse     │◀────│  200 {data}      │
└──────────────┘     └──────────────────────┘     └──────────────────┘

Set PROXY_TO_BASE_URL to your backend’s base URL and add pay-per-call routes to ROUTES:

docker run \
  -e KEY0_WALLET_ADDRESS=0xYourWallet \
  -e PROXY_TO_BASE_URL=https://api.yourdomain.com \
  -e ROUTES='[{"routeId":"weather-query","method":"GET","path":"/api/weather/:city","unitAmount":"$0.01","description":"Current weather — $0.01 per call"}]' \
  -p 3000:3000 \
  key0ai/key0:latest

When PROXY_TO_BASE_URL is set:

Pay-per-call routes are handled by the proxy — agents call the route directly, Key0 settles and forwards to PROXY_TO_BASE_URL + path.
Subscription plans still call ISSUE_TOKEN_API as normal.
Routes and plans can coexist in the same config.

Key0 injects payment metadata headers on every proxied request so your backend can log or verify the payment without a round-trip:

Header	Value
`x-key0-tx-hash`	On-chain transaction hash
`x-key0-plan-id`	Plan that was charged
`x-key0-amount`	Dollar amount (e.g. `"$0.01"`)
`x-key0-payer`	Payer wallet address (when available)

ISSUE_TOKEN_API is not called for pay-per-call routes when PROXY_TO_BASE_URL is set. You can omit it entirely if all you are selling is route access.

Test it

Once the container is running, verify the setup:

Check the agent card

curl http://localhost:3000/.well-known/agent.json

Expected output

{
  "name": "My Service",
  "description": "Payment-gated API",
  "url": "http://localhost:3000",
  "skills": [{ "id": "basic", "name": "Basic plan" }]
}

Browse available plans

curl http://localhost:3000/discover

Expected output

{
  "agentName": "My Service",
  "description": "Payment-gated API",
  "plans": [
    { "planId": "basic", "unitAmount": "$0.10", "description": "Basic plan" }
  ],
  "routes": []
}

Request access to a plan (returns 402 challenge)

curl -X POST http://localhost:3000/x402/access \
  -H "Content-Type: application/json" \
  -d '{"planId": "basic"}'

Expected output (HTTP 402)

{
  "x402Version": 2,
  "accepts": [{ "amount": "100000", "payTo": "0xYourWallet...", "network": "eip155:84532" }],
  "challengeId": "http-a1b2c3d4-...",
  "error": "Payment required"
}

The discovery call returns all available plans — start here to find a valid planId. The access request returns an x402 challenge with the payment amount and destination wallet. An agent completes the flow by signing an EIP-3009 authorization and submitting proof. See Paying for Access for the full client walkthrough. If you have pay-per-call routes configured (with PROXY_TO_BASE_URL), test the route flow by calling the route directly:

Request a paid route (returns 402 challenge)

curl http://localhost:3000/api/weather/london

Expected output (HTTP 402 — same as subscription)

{
  "x402Version": 2,
  "accepts": [{ "amount": "10000", "payTo": "0xYourWallet...", "network": "eip155:84532" }],
  "challengeId": "http-a1b2c3d4-...",
  "error": "Payment required"
}

After payment, the server returns a ResourceResponse with your backend’s data instead of an AccessGrant. See Paying for Access — Per-Request Flow for the full client walkthrough.

Docker image tags

Tag	When to use
`latest`	Latest stable release
`1.2.3` / `1.2` / `1`	Specific version pinning for production
`canary`	Latest main branch build (for testing)

Next steps

Environment Variables

Full reference of all configuration options including PROXY_TO_BASE_URL.

Pay-Per-Request Standalone Example

Runnable example: Key0 as a payment gateway proxying to a backend API.

Storage Configuration

Redis, Postgres, and custom storage backends.

Automatic Refunds

How Key0 handles failed deliveries with on-chain refunds.

Getting Started

Protocols

Architecture

Integrations

Guides

Deployment

Standalone Docker

Option A: Setup UI (zero-config start)

Docker Compose profiles

Option B: Environment variables

ISSUE_TOKEN_API contract

Pay-Per-Call Routes (PROXY_TO_BASE_URL)

Test it

Docker image tags

Next steps

Environment Variables

Pay-Per-Request Standalone Example

Storage Configuration

Automatic Refunds

Getting Started

Protocols

Architecture

Integrations

Guides

Deployment

​Option A: Setup UI (zero-config start)

​Docker Compose profiles

​Option B: Environment variables

​ISSUE_TOKEN_API contract

​Pay-Per-Call Routes (PROXY_TO_BASE_URL)

​Test it

​Docker image tags

​Next steps

Environment Variables

Pay-Per-Request Standalone Example

Storage Configuration

Automatic Refunds

Option A: Setup UI (zero-config start)

Docker Compose profiles

Option B: Environment variables

ISSUE_TOKEN_API contract

Pay-Per-Call Routes (PROXY_TO_BASE_URL)

Test it

Docker image tags

Next steps