---
title: Fee payer API
description: "Tempo gas sponsorship for user transactions"
---

# Fee payer API

The fee payer endpoint sponsors transaction fees for users on the Tempo network. Users can send transactions without holding gas tokens — the platform pays fees from an operator wallet.

This endpoint works with the [MPP payment flow](/payments/mpp) and the [Tempo wallet integration](/api-reference/wallet#tempo-balance-query).

## Sponsor a transaction

```http
POST /api/fee-payer
```

Accepts a Tempo transaction and sponsors its gas fees. The request body is forwarded to the `Handler.feePayer` handler from `tempo.ts/server`.

### Request

The request body should be a JSON object containing the Tempo transaction to sponsor. The exact format is defined by the `tempo.ts` SDK.

### Response

On success, returns the result from the fee payer handler (format defined by `tempo.ts`).

### Errors

| Code | Description |
|------|-------------|
| 503 | Fee payer not configured. The `TEMPO_FEE_PAYER_KEY` environment variable is not set. |

## Check fee payer status

```http
GET /api/fee-payer
```

Returns the current status and network configuration of the fee payer.

### Response

```json
{
  "status": "ready",
  "chain": "Tempo",
  "chainId": 4217
}
```

### Response fields

| Field | Type | Description |
|-------|------|-------------|
| `status` | string | `ready` when the fee payer is configured, `disabled` otherwise |
| `chain` | string | Network name (`Tempo` or `Tempo Testnet`) |
| `chainId` | number | Chain ID (`4217` for mainnet, `42431` for testnet) |

<Note>The network is determined by the `TEMPO_TESTNET` environment variable. When set to `true`, the fee payer uses the Tempo testnet (chain ID `42431`).</Note>

## How gas sponsorship works

Tempo supports protocol-level gas sponsorship. When a user submits a transaction through this endpoint:

1. The user signs their transaction normally.
2. The transaction is sent to the fee payer endpoint.
3. The operator wallet pays the gas fee on behalf of the user.
4. The transaction is submitted to the Tempo network.

This removes the need for users to hold native gas tokens and reduces friction for on-chain payments.
