---
title: "Create a decider"
method: POST
path: "/v1/projects/{project_id}/deciders"
tags: ["Deciders"]
---

# Create a decider

`POST /v1/projects/{project_id}/deciders`

## Request

- Base URL: `https://api.naturali.ai`
- URL: `https://api.naturali.ai/v1/projects/{project_id}/deciders`
- Auth: one of:
  - HTTP bearer
  - OAuth 2 (authorization code, authorization URL `https://api.naturali.ai/authorize`, token URL `https://api.naturali.ai/token`, scopes: `mcp:access`)

Creates a decider at version 1: a named question set and the backend that answers it, exactly one of `agent_id` and `tool_id`. Every question declares a finite answer space, validated here. The backend must be in the decider's project. An agent must carry no tool surface — no tool binding left active by `active_tool_ids` and no `knowledge_config.write_memory_store_id` — or the create is refused with `400 DECIDER_AGENT_NOT_TOOL_LESS`. A tool must be `http` or `pipeline` and must not pin `input` or `questions` in its `preset_parameters`, or the create is refused with `400 DECIDER_TOOL_NOT_CALLABLE`. A duplicate `name` in the project is `409 NAME_CONFLICT`.

## Request body

- CreateDeciderRequest: Names exactly one of `agent_id` and `tool_id`.
  - `name` string, required: Human-readable name, unique per project
  - `description` string, nullable
  - `agent_id` string: A tool-less agent that answers
  - `tool_id` string: An http or pipeline tool that answers
  - `questions` DeciderQuestion[], required: The questions, in the order the model is shown them.
    - `type` 'predicate' | 'choice' | 'score', required
    - `name` string, required: Names the question's answer. Unique within the set; starts with a letter or underscore and holds only letters, digits and underscores (at most 64).
    - `instructions` string, required: What to judge
    - `choices` DeciderChoice[]: A `choice` question's options; required for `choice` only
      - `value` string, required: What a `choice` answer carries; unique within the question
      - `description` string, required
    - `levels` DeciderLevel[]: A `score` question's ordered levels; required for `score` only
      - `label` string, required
      - `description` string, required
  - `version_label` string: Optional tag for version 1, e.g. `initial`

## Response `201`

Decider created

- Decider
  - `id` string
  - `project_id` string
  - `name` string
  - `description` string, nullable
  - `agent_id` string, nullable: The tool-less agent that answers; null when a tool does
  - `tool_id` string, nullable: The http or pipeline tool that answers; null when an agent does
  - `version` integer: The question set's version. Bumped only by a write that changes `questions`.
  - `questions` DeciderQuestion[]: The questions, in the order the model is shown them.
    - `type` 'predicate' | 'choice' | 'score', required
    - `name` string, required: Names the question's answer. Unique within the set; starts with a letter or underscore and holds only letters, digits and underscores (at most 64).
    - `instructions` string, required: What to judge
    - `choices` DeciderChoice[]: A `choice` question's options; required for `choice` only
      - `value` string, required: What a `choice` answer carries; unique within the question
      - `description` string, required
    - `levels` DeciderLevel[]: A `score` question's ordered levels; required for `score` only
      - `label` string, required
      - `description` string, required
  - `created_at` string, date-time
  - `updated_at` string, date-time

## Other responses

- `400`: Bad request — invalid questions, an unknown or tool-bearing agent
- `401`: Unauthorized
- `403`: Forbidden
- `409`: A decider with this name already exists in the project

---

[API](https://skmtc.dev/naturali/apis/naturali-ai-api.md) · [All operations](https://skmtc.dev/naturali/apis/naturali-ai-api/llms.txt) · [OpenAPI document](https://skmtc.dev/naturali/apis/naturali-ai-api/revisions/e4905b78f422?raw)