Validating Slot Values

This guide covers the different ways you can validate slot values returned after a collect step in a flow. Simple validations can be defined in the flow step itself, while validations requiring external data are performed by a custom action.

Validating a Phone Number#

Assume that your assistant has a flow allowing users to change the phone number associated with their account. Note that the description field of the collect step already provides information to the Command Generator about the desired format.

Validating a Slot Value's Format with a Condition#

Rejections are a lightweight way to do simple validation of extracted slot values. Add a rejections field to your collect step to validate the phone number extracted by the LLMCommandGenerator, and to reject the value if it does not match. This example uses a regular expression, but you can use any condition.

Remember to add a corresponding response to your domain to inform the user that their phone number wasn't collected successfully. Afterwards, the user will be asked for their phone number again.

Validating a Slot Value Against a Database or API#

If you need more advanced logic to decide whether to accept a slot value, you can use a custom action instead of a rejection. For example, you can use a custom action if you need external data to know if a slot value is valid. This example checks whether there is already another account associated with this phone number.

To do this, add an action step to your flow, with next conditions to handle the branching logic. First, create a custom action to call the API:

This example action uses the hash of the number to determine the outcome, so that you can use fixtures to write deterministic end-to-end tests.

And add a boolean slot called phone_number_has_account to your domain, along with a response to send in case the phone number is already associated with another account. Also add the name of the custom action to the domain:

Now, add a new step to your flow to call this custom action. Create a condition in the next field of this step to branch based on the phone_number_has_account slot. If the number already has an account, your assistant will inform the user, unset the phone_number slot, and return to the start of the form. In order to jump back to the beginning of the form, add an "id" field to the first step in the flow. Your flow should now look like this: