---
page_type: error
code: 21656
message: "21656: The ContentVariables Parameter is invalid"
level: ERROR
product: Programmable SMS
---

## Description

The ContentVariables Parameter is invalid.

### Possible Causes

- The ContentVariables Parameter is not a JSON String.
- A ContentVariables variable placeholder is improperly formed e.g. {{example}.
- A ContentVariables variable placeholder is an "empty mustache" e.g. {{}}.
- The ContentVariables field is defined with improper formatting at time of send.
- The ContentVariables field contains a variable that was set to null or empty string at time of send.

### Possible Solutions

- Review the [documentation](/docs/content/using-variables-with-content-api) on how to use Content Variables with Content Templates.
- Validate the ContentVariables Parameter, it must be a JSON String and be properly formatted.
- Make sure all ContentVariables are defined and have a valid definition at time of send. ContentVariables cannot be an empty string or null.