---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/api/errors/57008#article
headline: "57008: 'EventType' format must be String"
url: https://www.twilio.com/docs/api/errors/57008
inLanguage: en
dateModified: 2026-03-26T11:40:11.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# 57008: 'EventType' format must be String

Log Type: APPLICATION

Log Level: ERROR

## Description

Twilio returns this error when the request includes `EventType`, but the value is not a string. This code appears in the Messaging error dictionary.

### Possible causes

* `EventType` was sent in a format other than a string.
* The request payload was built or serialized incorrectly, so `EventType` did not reach Twilio as a string.

### Possible solutions

* Pass `EventType` as a string value in the request.
* Review the code that builds the request payload and make sure `EventType` stays a string before you send it.
* Check the error logs to inspect the exact request that Twilio received.

#### Additional resources

* [Programmable Messaging](/docs/messaging)
* [Message resource](/docs/messaging/api/message-resource)
* [Debugging Your Twilio Application](/docs/usage/troubleshooting/debugging-your-application)