System One API (Noul, Choice, Score)

A call to the System One API has three parts: the model to use, a state (the text or structured data to be judged) and a set of named questions. The response returns the answers keyed by question name, along with token usage. Nothing in the response is free-form text.

TypeSafe's documentation defines three question types. A noul question is yes/no and its answer is a probability. A choice question gives a set of options, each with a short description, and the answer is the chosen option with its probability; TypeSafe says up to 255 options are supported. A score question gives an ordered list of levels, described one by one, and the answer places the input on that scale.

Because the caller declares every allowed answer up front, the response cannot contain a value outside the declared set. That guarantees the shape of the answer, not that it is the right answer.

How it works

The request is a POST to TypeSafe's System One endpoint with an API key sent as a bearer token. Every question in the request is evaluated in parallel against the same state, so adding more questions to one call does not multiply latency the way sequential LLM calls would. TypeSafe publishes a Python SDK and a JavaScript SDK, and the docs also list a plugin for Claude Code. The API is in early access, so field names and limits can change; the current TypeSafe documentation is the reference.

Example

An illustrative request shape (not a copy of TypeSafe's docs) that triages a support message with all three question types:

{
  "model": "jev-latest",
  "state": "I was charged twice this month, please fix it today.",
  "questions": {
    "wants_refund": {"type": "noul", "instructions": "Does the customer ask for money back?"},
    "team": {"type": "choice", "instructions": "Which team handles this?",
             "criteria": {"billing": "Charges and refunds", "support": "Bugs and how-to"}},
    "urgency": {"type": "score", "instructions": "How urgent is it?",
                "criteria": ["Can wait", "Reply today", "Blocking now"]}
  }
}

Common misconceptions

FAQ