If you ever have occasion to experiment with a know-to-be-working and standards compliant IMS Basic LTI tool then please consider reading Dr Chuck’s “Sakai LTI Unit Tests” blog post.
Dr Chuck has written an LTI tool that can be used for testing or for a sanity check. Here are the key facts:
URL: https://online.dr-chuck.com/sakai-api-test/tool.php Key: 12345 Secret: secret
If you are unclear about any of the above then an earlier blog post about IMS Basic LTI may help explain things.