> For the complete documentation index, see [llms.txt](https://docs.hyperlink.xyz/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.hyperlink.xyz/api/api-keys.md).

# Authentication & Keys

HyperLink authenticates every request with an **EIP-712 signature**, not bearer tokens or API secrets. An API key is an approved **agent wallet**: a keypair your master account authorizes to sign trading actions and read queries on its behalf.

HyperLink is a prime broker for Hyperliquid. It mirrors Hyperliquid's agent model and EIP-712 signing, so existing Hyperliquid tooling works against the HyperLink base URL. For a working signed-request example, see [API Quickstart](/api/setup.md).

## How it works

The agent private key signs each request; the enclave verifies the agent is approved by your master account, then executes. There are no shared secrets.

## Create an API key

### In the web app

1. Connect your master wallet to the [web app](https://app.hyperlink.xyz).
2. Go to **Settings → API** and click **Generate**.
3. Copy and securely store the private key. It is shown **once** and cannot be recovered.

### With the approveAgent action

Generate the agent keypair locally, then approve its address with an `approveAgent` action signed by your **master account** (agents cannot approve other agents). The full schema is in [Exchange Methods](/api/exchange-methods.md).

## Limits and permissions

| Limit                      | Value         |
| -------------------------- | ------------- |
| Named agents per account   | 5             |
| Unnamed agents per account | 1             |
| Agent name length          | 64 characters |

Agents **can** place and cancel orders, update leverage and margin, and run read queries. Agents **cannot** withdraw funds, approve or revoke other agents, or run master-account transfer actions such as `sendAsset` and `usdClassTransfer`. Those require your master account's own user-signed signature. A `readOnly` agent can query but not trade.

## Signing

Each request to `/exchange` (and each WebSocket subscription) carries an EIP-712 signature plus a millisecond `nonce`. There are two signing domains; an SDK selects the right one per action.

| Scheme            | EIP-712 domain               | `chainId` | Used for                                                                   | Signed by               |
| ----------------- | ---------------------------- | --------- | -------------------------------------------------------------------------- | ----------------------- |
| Agent (L1 action) | `Exchange`                   | `1337`    | Orders, cancels, margin, leverage, agent transfers, queries, subscriptions | Agent or master account |
| User-signed       | `HyperliquidSignTransaction` | `42161`   | `withdraw`, `approveAgent`, `usdClassTransfer`, `sendAsset`                | Master account only     |

Both domains use `version` `"1"` and `verifyingContract` `0x0000000000000000000000000000000000000000`.

{% hint style="warning" %}
These signing `chainId` values (`1337`, `42161`) are Hyperliquid-compatible EIP-712 domain values, **not** the HyperEVM network chainId (`999`). Use the network chainId only for direct on-chain contract calls, such as staking.
{% endhint %}

**Nonces:** set `nonce` to the current Unix time in milliseconds. Each is single-use per signer; a nonce older than 2 days or more than 1 day in the future is rejected.

{% hint style="info" %}
Sign with an SDK, not by hand. A bad signature recovers a different address and fails with an unhelpful `"User or API Wallet … does not exist"`. The Hyperliquid SDKs ([TypeScript](https://github.com/nktkas/hyperliquid), [Python](https://github.com/hyperliquid-dex/hyperliquid-python-sdk)) implement both schemes correctly, and the Hyperliquid [signing reference](https://hyperliquid.gitbook.io/hyperliquid-docs/for-developers/api/signing) applies unchanged.
{% endhint %}

Common causes of signing failures: wrong scheme for the action, field-order or encoding mismatches, trailing zeroes on numeric string fields, or upper-case address characters (lowercase addresses before signing).

## Revoke an API key

1. Open **Settings → API** in the [web app](https://app.hyperlink.xyz).
2. Find the agent by name or address.
3. Click **Revoke** and sign with your **master wallet**.

A revoked agent can no longer access your account.

## Next steps

* [API Quickstart](/api/setup.md): base URLs, envelope, and a working example.
* [Exchange Methods](/api/exchange-methods.md): actions, queries, and schemas.
* [WebSocket API](/api/websocket.md): real-time subscriptions.


---

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