So, if I understand correctly, "Operatoren" are more-or-less equivalent to what I think of as the "question verbs" or "task verbs" (analyze, discuss, criticize, etc.) used in the free-response questions of tests, and the "Definitionen" are brief descriptions of what test-takers are expected to do in their answers to questions using those verbs. If Operatoren are always verbs, then "task verbs" would be perfect for AE, at least. If Operatoren are not all verbs, this solution will not work.
In a US standardized test, one might see a question like "draw a conclusion about the cause and effect relationship in the occurences described in the passage above". There, the task verb is "draw a conclusion", but the key to this question is actually "cause and effect".
I am not aware of a broader term (i.e. covering more than verbs) that standardized testing bodies use, but that certainly does not mean there isn't one. In a pinch though, task descriptor/identifier/keyword all sound like acceptable suggestions to me.
Cf. the following (link above) from the official description of a voluntary standardized examination in the subject of government and politics for high-school students in the US.
The following task verbs are commonly used in the free-response questions:
Compare: Provide a description or explanation of similarities and/or differences.
Define: Provide a specific meaning for a word or concept.
Describe: Provide the relevant characteristics of a specified topic.
Develop an argument: Articulate a claim and support it with evidence.
Draw a conclusion: Use available information to formulate an accurate
statement that demonstrates understanding based on evidence.
Explain: Provide information about how or why a relationship, process, pattern,
position, situation, or outcome occurs, using evidence and/or reasoning.
Explain “how” typically requires analyzing the relationship, process, pattern,
position, situation, or outcome, whereas explain “why” typically requires
analysis of motivations or reasons for the relationship, process, pattern,
position, situation, or outcome.
Identify: Indicate or provide information about a specified topic, without
elaboration or explanation.