# 12200: Schema validation warning

Log Type: APPLICATION

Log Level: WARNING

## Description

### Schema validation warning

The provided XML does not conform to the Twilio Markup XML schema. Please refer to the specific error and correct the problem.

### Possible causes

* Misspelled verbs
* Incorrect case for verbs; TwiML is case-sensitive, so `<Say>` works, but `<say>` will not
* Misspelled or unknown attributes
* Unknown or unexpected nested elements.

### Possible solutions

* Check the line and column reported by the warning to see what part of your XML response caused the complaint
* Verify that your application server is accepting and properly responding to any [custom parameters](https://support.twilio.com/hc/en-us/articles/115011213347) you may be passing