In External Tools, value is set to 100 by default, but there's no ability to change the value. We use VoiceThread, for example, and the folks at VT indicate they do not currently support grading through the tool.
Not all external tools handle send grades or determine the grade value. This can cause external tools to have more weight than Moodle modules.
Create a course category with a forum and an external tool. Simple weighted means. Assume desire is to use external tool as another type of forum (that's what we're doing w/ VT.), worth 10 points each.
Set forum scale to 10 points.
External remains at 100.
As a student, participate in forum and external tool.
As a teacher, grade 10 points to both forum and external tool.
Check gradebook. Student only has 18.18% grade, whereas it should be 100%.
There was a mention in
MDL-20534, but I'm not sure if it was examined further.
I can work around it myself, but many of our faculty struggle with the concept.