Every /v1 route now needs an API key. Send it as Authorization: Bearer sk-ms-..., and read Authentication. Each organization also gets a request and an input-token limit per minute, with x-ratelimit-* headers on every response. See Limits and rate limits.
POST /v1/decision-machine-1/classify-tree walks a nested label tree in one request. It runs classify once per level on the same text, then descends into the winning label. The response carries the path, the compound probability and confidence, and every level with its own scores, input size and inference time. See Classify tree.