Drex (Decision Model)

curl -s -X POST "$NDI_BASE_URL/v1/systemone" \
  -H "X-API-Key: $NDI_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"state":"Invoice INV-1844 bills 240 bearings at £4.80; the purchase order allows 200 at £4.15.","questions":{"matches_po":{"type":"noul","instructions":"Does the invoice match its purchase order?"},"exception":{"type":"choice","instructions":"What is the main exception?","criteria":{"none":null,"price_variance":"A unit price is above the purchase order.","quantity_variance":"A quantity is above the purchase order."}},"disposition":{"type":"score","instructions":"How should accounts payable treat it?","criteria":["pay","review","hold","reject"]}}}'

{
  "model": "nace-ai/drex-v1.5",
  "answers": {
    "matches_po": { "type": "noul", "noul": 0.04 },
    "exception": {
      "type": "choice",
      "choice": "price_variance",
      "confidence": 0.66,
      "probabilities": { "none": 0.02, "price_variance": 0.71, "quantity_variance": 0.27 }
    },
    "disposition": {
      "type": "score",
      "score": 1.3,
      "legend": ["pay", "review", "hold", "reject"],
      "probabilities": { "0": 0.03, "1": 0.64, "2": 0.30, "3": 0.03 },
      "confidence": 0.61
    }
  },
  "usage": { "input_tokens": 212, "output_tokens": 186 },
  "evaluation_time_ms": 184.0,
  "request_id": "4f1c…"
}

​

Limits and input rules

• A call carries 1 to 512 questions. A choice lists 1 to 255 options, and a score 1 to 255 levels.
• The state and questions together must fit the decision model’s context. A longer request is refused with 422 at path state.
• Question names are trimmed, and each answer comes back under the trimmed name. A blank name is refused.
• Unknown fields are refused, except model, which is accepted and ignored: the deployment chooses the decision model.
• A NUL character (\u0000) anywhere in the body is refused.
• Nothing is stored, so sending the same call again is safe. The SDKs do not retry it on their own; retry a 429 after Retry-After, and a 503.

​

Errors

• 401 unauthorized — the X-API-Key header is missing or the key is invalid. This endpoint does not accept Authorization: Bearer.
• 422 invalid_request — the body does not match the schema, or the state and questions are too long for the decision model. Besides the usual detail.errors, the error carries detail.issues: one {path, message} per refused field, by dotted path (state, questions.exception.criteria). detail.errors[].loc starts with body and includes the question’s type (["body", "questions", "exception", "choice", "criteria"]); detail.issues paths leave both out.
• 501 not_implemented — this deployment has no decision model.
• 429 rate_limited — the account’s request or concurrency budget is spent.
• 503 upstream_unavailable — the decision model is unavailable or did not answer within 45 seconds; retry.