> For the complete documentation index, see [llms.txt](https://developers.shredpay.xyz/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://developers.shredpay.xyz/agent-wallet/concepts/gas-model.md).

# Gas Model

Two ways to pay for gas. Knowing which applies to which call is the difference between "this transaction worked" and "out of funds."

| Mode                  | Who pays                                                  | When it applies                                                                                                  | Service fee                                         |
| --------------------- | --------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------- | --------------------------------------------------- |
| **Agent pays**        | The sub-wallet's own native balance (ETH, BNB, MATIC, …). | `send_transaction` and any direct call you make through `POST /api/tx/send`.                                     | None.                                               |
| **ShredPay sponsors** | ShredPay's gas wallet on the target chain.                | `execute_swap`, `defi_deposit`, `defi_withdraw`, `gas_swap` — all flows that go through the **Router** contract. | A small fee on the input amount, in the same token. |

## Why two modes

Agents need to be able to call arbitrary contracts (paying their own gas keeps the model simple and uncensorable). But the most common operations — swaps, deposits, withdrawals — go through ShredPay's Router contract, which can batch token approvals and the actual call into a single sponsored transaction. That's faster, cheaper, and avoids the "agent has USDC but no ETH for gas" footgun.

## When you must hold native gas

Any time you call `send_transaction`. Typical examples:

* ERC-20 transfers to addresses outside the Router.
* Direct calls to a third-party protocol that ShredPay does not have a Router pathway for.
* Any custom calldata.

If your sub-wallet runs out of native gas mid-flow, use [`gas_swap`](/agent-wallet/guides/gas-management.md) — it converts USDC to ETH through the Router with **ShredPay** paying gas, so the agent doesn't need ETH to obtain ETH. This is how an agent funded only in USDC bootstraps itself.

> **Today `gas_swap` is supported on Base only.** Plan accordingly if your agent operates on other chains — pre-fund native gas or hold the agent on Base.

## When ShredPay sponsors

Any time you call:

* `execute_swap` — swap one token for another.
* `defi_deposit` / `defi_withdraw` — vault interactions in the curated DeFi catalog.
* `gas_swap` — bootstrap native gas from USDC.

These calls only succeed on chains where the **Router** contract is deployed. Check `has_router` in `GET /api/wallet/chains`:

```json
{
  "chains": [
    { "id": 1,     "name": "Ethereum", "has_router": false },
    { "id": 8453,  "name": "Base",     "has_router": true  },
    { "id": 42161, "name": "Arbitrum", "has_router": false }
  ]
}
```

A sponsored call on a chain without Router returns `400 ROUTER_NOT_AVAILABLE`.

## Service fees

Sponsored flows charge a small fee (basis points on the input amount, taken in the same token). Fees are returned in every quote — they are never a surprise:

```json
{
  "amount_in": "100000000",
  "amount_out": "0.0473...",
  "fee_amount": "100000",
  "fee_token": "USDC",
  "gas_sponsored": true
}
```

For exact current fee schedules, check the response body of `POST /api/swap/quote` — they are sourced live, not from documentation.

## Gas estimation

```http
GET /api/gas/estimate?chain_id=8453
```

```json
{
  "chain_id": 8453,
  "gas_price_wei": "1000000",
  "recommended_eth_for_5_txs": "0.0005",
  "native_balance_wei": "120000000000000"
}
```

Use this to decide whether the wallet has enough headroom for the next few transactions, or whether to swap up first.

## Related

* [Manage Gas guide](/agent-wallet/guides/gas-management.md) — how to keep the wallet topped up
* [Multi-chain](/agent-wallet/concepts/multi-chain.md) — which chains have Router


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://developers.shredpay.xyz/agent-wallet/concepts/gas-model.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.