> For the complete documentation index, see [llms.txt](https://docs.endless.link/endless/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.endless.link/endless/devbuild/technical-documentation/sponsored-transaction.md).

# Sponsored Transaction

#### Sponsored Transactions

Sponsored transactions on the Endless chain refer to transactions where the gas fees are paid by the contract invoked by the transaction.

On the Endless blockchain, executing transactions requires a fee, also known as a gas fee, which is typically paid in the native token of the Endless chain (EDS). Gas fees are paid to the validators of the Endless chain to ensure network security. However, for new users, especially those transitioning from Web 2.0, this requirement can increase the barrier to entry.

Sponsored transactions lower the difficulty of interacting with contracts for users, particularly beginners. By leveraging sponsored transaction technology, contracts can make it easier for users to interact while ensuring the contract itself covers the gas fees, thereby maintaining stable chain operations.

#### Use Cases

* Scenario 1 (under construction)
* Scenario 2 (under construction)

#### Sponsored Contract Functions

Sponsored transactions are implemented at the contract level. Any contract function intending to offer this feature can include the sponsored keyword before the function declaration. This instructs the VM to mark the function as a "sponsored contract function."

Below is an example:

```rust
entry sponsored fun fund(dst_addr: &signer) {
    ...
}
```

When a transaction invokes the fund function, the gas fees for that transaction will be paid by the contract. Ensure the contract account has sufficient funds to cover these fees; otherwise, the user will encounter an error indicating insufficient tokens to pay the gas fees when submitting the transaction.

{% hint style="danger" %}
Although sponsored functions are easy to implement, consider the following points before using them:

* Access Control
* External Calls Only
  {% endhint %}

**Access Control** Determine whether the contract function should be accessible to all users. If the function is intended to sponsor only specific users, implement user checks within the contract to exclude unwanted users. Failing to do so may result in unnecessary gas fee expenses.

**External Calls Only** Mark the contract function as an entry function to allow only direct user-initiated transactions to call it. Prevent external contracts from invoking the sponsored transaction function to guard against potential attacks.


---

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