> ## Documentation Index
> Fetch the complete documentation index at: https://hilos-40.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Adding temporary variables to a flow

This is an ideal scenario for using Flow Execution Variables. These variables are user-defined and can be included in the flow builder, sent via the API call body under the key `flow_execution_variables`. Note that these variables are global to a flow execution, not tied to a specific contact. If a flow execution involves multiple contacts, these variables will apply to all of them.

### Adding a Flow Execution Variable

To utilize flow execution variables, ensure your account has the feature flag enabled. Request activation through our support channel. Once activated, a new field will appear in the flow configuration. Here, you can input the desired variables within the API call. Enter the name and type, then save them.

![Flow execution variables filled](https://hilos-media.s3.us-east-2.amazonaws.com/mintlify/advanced/flows/flow-execution-variables/create-vars.png)

Now, you can select these variables within the flow.

![Using flow execution variables](https://hilos-media.s3.us-east-2.amazonaws.com/mintlify/advanced/flows/flow-execution-variables/use-vars.png)

### Formatting Your API Call

The API call for flow execution variables differs slightly from a standard API call. You must include a new key `flow_execution_variables` with an object containing the expected variable keys for the flow. Remember, these variables are not contact-specific. To assign different variables to various contacts, create multiple flow executions using separate API calls.

The API call should resemble:

```
POST https://api.hilos.io/api/flow
```

```json theme={null}
{
  "execute_for": "LIST",
  "contact_list": [
    {
      "phone": "+525544443333"
    }
  ],
  "flow_execution_variables": {
    "key": "value"
  },
  "has_priority": true
}
```