---
title: "Build a parameter set from a cell spec"
method: POST
path: "/model_builders/{model_builder_id}/build"
tags: ["Model builders"]
---

# Build a parameter set from a cell spec

`POST /model_builders/{model_builder_id}/build`

## Request

- Base URL: `https://api.ionworks.com`
- URL: `https://api.ionworks.com/model_builders/{model_builder_id}/build`
- Auth: none declared

Build the model's parameters for a cell spec; with ``save``, store them as a parameterized model.

## Path parameters

- `model_builder_id` string, uuid, required

## Request body

- BuildRequest: Body for building a parameter set from a cell spec.
  - `cell_spec_id` string, required
  - `save` boolean: Save the result as a parameterized model on the cell spec.
  - `name` string, nullable: Name for the saved parameterized model. Required with save.
  - `description` string, nullable
  - `set_as_default` boolean: Make the saved model the cell spec's default parameterized model.

## Response `200`

Successful Response

- BuildResult: A built parameter set, plus what (if anything) is still missing.
  - `parameters` object, required: Parameter values, in the parameterized-model storage format.
  - `missing` string[]: Parameters the model needs that the builder did not produce.
  - `issues` ReadinessIssueModel[]: Warnings from the readiness check.
    - `severity` 'error' | 'warning', required
    - `code` 'missing' | 'unit_mismatch' | 'wrong_shape' | 'ambiguous' | 'unsatisfied_input', required
    - `message` string, required
    - `parameter` string, nullable: Model parameter the issue affects.
    - `path` string, nullable: Dotted path in the cell spec, as in a mapping.
    - `element` string, nullable: Recipe element name.
  - `parameterized_model_id` string, nullable: The saved parameterized model, when save was set.

## Other responses

- `422`: Validation Error

## Changes

- **2026-10-22** `39d84bb8875e`: 1 info
  - endpoint added

[Operation history](https://skmtc.dev/ionworks/apis/ionworks-api/changes/model_builders/:model_builder_id/build/post.md)

---

[API](https://skmtc.dev/ionworks/apis/ionworks-api.md) - [All operations](https://skmtc.dev/ionworks/apis/ionworks-api/llms.txt) - [OpenAPI document](https://skmtc.dev/ionworks/apis/ionworks-api/revisions/abebbbc5f60a?raw)