To make the error more readable, the long value can be removed from the error message. The user can see it in the "Value" field.
Steps to reproduce:
1) Create item with type - HTTP agent
(fill URL with any link, f.e. https://www.zabbix.com/);
2) Press "Test" button;
3) In appeared form press - "Get value and test".
Result:
An error is too long and incomprehensible to the user.

Expected:
Such a large value could be shown partially and an ellipsis could be added. Anyone who wants to see entire message can see the value below in the “Value” field.
For example:
Value of type "string" is not suitable for value type "Numeric (unsigned)". Value "<!doctype html><html itemscope="" itemtype="fg"lang="lv"><head><meta content="text/html; charset=UTF-8" http-equiv="Content-Type"><meta content="/images ..."
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