Nonagon Link — API Provider Guide
A step-by-step guide to selling paid APIs to AI agents and earning USDC
1. What is Nonagon Link
Nonagon Link is an agentic payment gateway that lets AI agents autonomously pay for APIs with the USDC stablecoin. By registering as an API Provider, you automatically earn USDC revenue on every API call made by AI agents.
2. Getting Started
What you need
- An invitation code (closed beta — registration is invite-only)
- An email address
- The endpoint URL of the API you want to offer
If you would like to participate, please join the waitlist. We will send you the registration page details when you are invited.
Provider Dashboard URL
The Provider Dashboard URL is included in the invitation email we send you.
3. Account Registration
3-1. Open the registration page
Open the registration page provided with your invitation and enter the following:
| Field | Description | Required |
|---|---|---|
| Email address | Used for login | Required |
| Password | 8 characters or more | Required |
| Password (confirmation) | Same value as above | Required |
| Organization name | The name shown on the marketplace (labeled "Organization name" on the form) | Required |
| Invitation code | Issued by the Nonagon Link team. Codes use the NLINK-XXXX-XXXX-XXXX format | Required |
| CAPTCHA verification | Bot protection via Cloudflare Turnstile | Required |
| Agree to the Terms of Service | Checkbox must be checked | Required |
3-2. Store your API Key securely
After successful registration, your API Key (in nlink_sk_xxxxxxxx format) is displayed only once.
- This API Key will never be shown again
- Store it in a safe place (such as a password manager)
- The API Key is used to authenticate with the x402 payment APIs (such as
POST /api/payout/*). You log in to the dashboard with your email address and password
4. Login
Log in with your email address and password on the login page we shared with you.
- Sessions are managed with a JWT cookie
- Session lifetime: 1 hour (with automatic refresh)
- Forgot your password? Reset it from the "Forgot your password?" link on the login page
5. Creating an API Listing
Register your API from "API Management" → "Register New API" in the dashboard.
5-1. Choosing a Listing type
| Type | Description | Best suited for |
|---|---|---|
| proxy | Nonagon Link relays your API as a reverse proxy | The simplest option. Nonagon Link manages your API Key |
| x402_direct | The Provider implements the x402 protocol themselves | When your API already supports x402 |
| flexible_proxy | Proxies to any URL within an allowed domain list | APIs with multiple endpoints |
5-2. Common fields
| Field | Description | Constraints |
|---|---|---|
| API name | Shown on the marketplace | 1–120 characters |
| Category | API classification (e.g. weather, finance, ai) | 1–40 characters |
| Price (USDC) | Price per API call | Solana listings: 0.001–0.100 USDC / Ethereum listings: range varies by chain and asset |
| Description | Detailed description of the API | Up to 4,000 characters (Optional) |
| Documentation URL | Link to external documentation | HTTPS URL (Optional) |
5-3. Additional fields for the proxy type
| Field | Description | Constraints |
|---|---|---|
| Endpoint URL | Base URL of your API | HTTPS required |
| HTTP method | GET / POST / PUT / DELETE / PATCH | Required |
| Auth header name | Authentication header of the Provider API | e.g. Authorization, X-API-Key |
| API key | Authentication key of the Provider API | Securely stored and injected by Nonagon Link |
| Health check URL | URL for monitoring API availability | HTTPS (Optional) |
| Timeout (seconds) | Timeout for API calls | 5–120 seconds (default: 60) |
| Request schema | Input definition in JSON Schema format | (Optional) |
5-4. Automatic OpenAPI schema generation
Click the "Generate Schema" button on the API management screen and AI will automatically generate an OpenAPI schema for your endpoint. The generated schema is attached to the Listing and is referenced by AI agents to understand how to use your API.
5-5. Publishing a Listing
A newly created Listing is inactive (is_active: false). After reviewing its contents, switch it to "Active" from the settings screen. Once active, agents can call and pay for it.
Directory listing is controlled separately by is_listed (default: listed). Turning listing off does not stop the API — agents that already know its URL can still call it, which is useful for private-customer or in-review APIs.
6. Dashboard
6-1. Overview screen
| Metric | Description |
|---|---|
| Total calls | Total number of API calls across all Listings |
| Total revenue | Cumulative revenue in USDC |
| Total fees | Nonagon Link platform fees |
| Per-API statistics | Calls and revenue per Listing |
6-2. Per-Listing statistics
View detailed performance statistics for each Listing.
7. Payouts
7-1. Checking your balance
| Item | Description |
|---|---|
| Available balance | USDC/USD balance available for withdrawal requests |
| Processing | Amount currently being withdrawn |
| Exchange rate | Current USDC/USD rate |
7-2. Withdrawal flow
- Enter the withdrawal amount on the "Payouts" page
- A Nonagon Link administrator approves the request
- The transfer to your bank account is executed
- You receive a completion notification
Details such as withdrawal methods, currencies, and timing will be announced separately during the closed beta.
7-3. Setting a minimum payout amount
You can set a minimum payout amount (USD) on the payouts page. Withdrawal requests will not be executed until your balance reaches this amount.
8. Settings
8-1. Profile
View your display name and email address.
8-2. API Key management
- API Key rotation: Issue a new key with the "Regenerate API Key" button
- After rotation, the old key remains valid during a 24-hour grace period
- The old key is deactivated after the grace period
8-3. Bank account
Configure the bank account that receives your withdrawals.
9. How your API is called (x402 protocol)
Providers do not need to implement this directly, but this is useful background on how payments work.
For the proxy type
1. An AI agent sends a request to the Nonagon Link Proxy API
2. Nonagon Link verifies the x402 payment
3. On success, the request is forwarded to the Provider API with the auth header attached
4. The Provider API response is returned to the agent
5. USDC is added to the Provider's balanceNo implementation changes are required on the Provider side. Simply register your existing API as-is.
For the x402_direct type
The Provider must implement the x402 protocol (402 Payment Required responses) themselves. See the Agent Developer Guide for details.
10. FAQ
Q: I lost my API Key
A: Rotate your API Key from the settings screen. A new key will be issued.
Q: I want to delete a Listing
A: You can delete it from the API management screen. Deletion cannot be undone. You can also deactivate it to pause it temporarily, or keep it active but remove it from the directory.
Q: How much are the fees?
A: The pricing structure will be announced soon.
Q: Can I receive Japanese yen instead of USDC?
A: Details such as withdrawal methods and currencies will be announced separately.
Q: I want to register a test API and try it out
A: You can create a Listing and keep it inactive while reviewing its contents. You can also turn off directory listing before activating it, so the API works but never appears in the public directory. Please contact the team about using the test environment.