Context in.
A clear next step out.

A structured API for choosing, evaluating and scoring. Give FastCD the state of your application and the question you need answered.

Try the playground ↗Read the docs ⟶

Choice

Choose from 1–1024 candidates and inspect the distribution over the available options.

Multi-choice

Select multiple relevant options from up to 1024 candidates, with up to 256 selections.

Reasoning

Enable reasoning before a structured decision, with a configurable token budget.

Multimodal

Combine context with up to four images to make visually grounded decisions.

Noul

Get the probability of “yes” for a natural-language question about the current state.

Score

Evaluate against 1–1024 ordered criteria and receive the expected zero-based index.

ONE REQUEST. STRUCTURED ANSWERS.

Built to work
inside your application.

Use Bearer authentication and ordinary JSON. The response includes answers, candidate probabilities, raw logits, backbone and usage. Confidence measures distribution concentration, not calibrated accuracy.

{
  "model": "simplex-fastcd",
  "state": {
    "message": "I was charged twice for my subscription."
  },
  "questions": {
    "route": {
      "type": "choice",
      "instructions": "Choose the department best suited to help.",
      "criteria": {
        "billing": "Payments and invoices",
        "support": "Technical issues",
        "sales": "New purchases"
      }
    },
    "topics": {
      "type": "multi_choice",
      "instructions": "Select all relevant topics.",
      "criteria": {
        "billing": "Payment or invoices",
        "refund": "Reimbursement",
        "technical": "Technical errors"
      },
      "min_choices": 0,
      "max_choices": 2
    },
    "needs_refund": {
      "type": "noul",
      "instructions": "Does this message describe a potential duplicate charge?"
    },
    "urgency": {
      "type": "score",
      "instructions": "Assess how urgently this needs attention.",
      "criteria": [
        "low",
        "medium",
        "high"
      ]
    }
  },
  "reasoning": false,
  "reasoning_max_tokens": 128
}

Context in.A clear next step out.