> This page is for Release Notes.

> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://mailchimp.com/developer/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://mailchimp.com/developer/_mcp/server.

# Improved error messaging on malformed requests to the Members endpoint

Previously, if an object was passed as the value of the email field in a POST to the [Lists/members endpoint](/developer/marketing/api/lists/list-members), the server would return a 500 error. Now we return a 400 error with a clear error message.

We saw multiple occurrences of these errors in our logs. Ideally, badly formed requests shouldn’t return 500 errors, and we should give more information to callers when errors do occur.