# Facet

Facet builds a model for one narrow task, such as sorting support tickets or pulling fields out of invoices, and keeps it better than a frontier model at that task: more accurate, faster and cheaper. You describe the work; Facet does the prompt and machine learning work, checks every change, and shows plainly what got better and what got worse.

## Start

- **In the web app:** sign in at [facet.halfspacelabs.com](https://facet.halfspacelabs.com) and make a Task. See [Quickstart](/docs/quickstart).
- **From your agent:** connect Claude, Cursor, ChatGPT, Codex or VS Code to `https://facet.halfspacelabs.com/mcp`. See [Use Facet from an agent](/docs/agents).
- **From your app:** call a Task with the OpenAI SDK. See [Call a Task](/docs/call).

## When to use Facet

Use Facet when one narrow job runs often and a frontier model is slow, costly or not quite right at it: classifying, extracting, routing, rewriting in a house style, grading. Keep a frontier model for open-ended work that changes every time.

## Pages

- [Quickstart](/docs/quickstart): make a Task, call it, make it better
- [Concepts](/docs/concepts): Tasks, Asks, Changes, Expectations and Versions
- [Call a Task](/docs/call): the OpenAI-compatible API
- [Use Facet from an agent](/docs/agents): the MCP server, sign-in, toolsets and every tool
- [The /v1 API](/docs/api): the API the web app and MCP tools use