---
title: "System One — AI agent routing with an open-source SDK and AI decision API "
description: "Build AI agent decisions with an open-source TypeScript SDK and a hosted decision API. Turn text and application state into choices, scores, and probabilities for tool routing, ranking, and condition checks."
canonical: "https://system-one.dev/en"
language: "en"
---

# System One — AI agent routing with an open-source SDK and AI decision API 

Build AI agent decisions with an open-source TypeScript SDK and a hosted decision API. Turn text and application state into choices, scores, and probabilities for tool routing, ranking, and condition checks.

## System One SDK

The open-source TypeScript SDK for AI agent decisions. Define questions, connect a model service, and handle typed choices, scores, and probabilities.
## System One API

A hosted AI decision API for routing, ranking, and condition checks. Call models over HTTP and manage API keys, usage, and credits from one console.
## Build with the SDK. Run on the API.

Use the SDK to define questions and handle typed results. Connect it to System One API for hosted inference, or configure a supported provider directly. Your code controls what happens next.
## A System One layer in your Agent workflow

Break broad tasks into explicit questions, then combine model judgments with deterministic rules in code.
## Route tools and tasks

Use Choice to select a tool or handling path from the options you define. Route uncertain cases to a reasoning model or human review.

[Build tool routing in TypeScript](https://docs.system-one.dev/en/docs/agent-integration)
## Rank and prioritize

Use Score to rate relevance, urgency, or quality against your rubric. Sort results and prioritize work using the returned scores.

[Choose a scoring rubric](https://docs.system-one.dev/en/docs/primitives)
## Check conditions

Use Noul to check intent, policy conditions, or whether a task is complete. Combine the probabilities with rules in your code.

[Understand yes/no probabilities](https://docs.system-one.dev/en/docs/primitives)

## Start here

- [Developer documentation](https://docs.system-one.dev/en)
- [Versioning and deprecation](https://docs.system-one.dev/en/docs/api/versioning)
- [Idempotency and retries](https://docs.system-one.dev/en/docs/api/idempotency)
- [API errors](https://docs.system-one.dev/en/docs/api/errors)
- [TypeScript SDK](https://system-one.dev/en/sdk)
- [API reference](https://system-one.dev/en/api)
- [Models](https://system-one.dev/en/models)
- [Model catalog](https://docs.system-one.dev/en/docs/models)
- [Authentication](https://system-one.dev/en/auth.md)
- [Pricing](https://system-one.dev/en/pricing)
- [Credit billing](https://docs.system-one.dev/en/docs/billing)
- [OpenAPI specification](https://system-one.dev/openapi.json)
- [Agent integration guide](https://system-one.dev/en/skill.md)
- [System One for Coding Agents: Cursor, Claude Code, Codex](https://docs.system-one.dev/en/docs/coding-agents)
- [Installable coding-agent skill](https://system-one.dev/skills/system-one/SKILL.md)
- [About](https://system-one.dev/en/about)
- [Contact](https://system-one.dev/en/contact)
- [Playground samples](https://system-one.dev/en/demo)
- [Blog](https://system-one.dev/en/blog)
- [SDK source](https://github.com/ziyu/system-one-sdk)
- [@system-one-ai/core (npm)](https://www.npmjs.com/package/@system-one-ai/core)