Can I add a custom classifier for my own agent?

Yes. Custom classifiers sit next to the built-ins and use the same mechanism: a threshold, a confidence, a finding when a trace crosses it. What differs is what they’re tuned to. A built-in like frustration runs a generic signal across every customer; a custom one is fitted to your agent’s own failure modes instead, the kind specific enough that no generic check was ever going to catch it: a tool answering with stale data, a retrieval step that silently drops a citation, a step your agent skips under one particular input shape.

The limit is the same one every classifier carries. A custom classifier still scores one narrow property, not the whole turn, and it still writes a finding rather than a verdict. Tuning it to your agent’s failure modes makes it more likely to fire on the right thing; it doesn’t turn it into a judgment on whether the agent succeeded.