System One API

Hosted API returning structured choices, scores and probabilities for AI agent decisions

Free trialsystem-one.devUpdated 25 Oct 2026

About System One API

System One is a hosted API and open-source TypeScript SDK for bounded decisions inside AI agents and applications. A single endpoint (POST /v1/systemone) takes a shared "state" such as a customer message, plus up to 32 questions, and returns structured answers: a selected option with a probability for each option (Choice), a score on a 2-10 level rubric (Score), or a yes/no probability (Noul). Your application decides what to do with the result; the service does not execute tools.

Best for

Routing and triage of requests
Ranking candidates against a rubric
Gating agent actions with yes/no checks
Support triage: Route an incoming message such as a billing complaint to the right team.
Tool routing: Let an agent choose which tool or workflow step to run next.
Candidate ranking: Score items against a rubric to rank them.
Gated agent checks: Run a yes/no check before an agent takes an action.

Not ideal for

Open-ended text generation
Workloads needing published uptime or latency guarantees
Non-technical users

Popular with

Developers
AI agent builders
Backend engineers

Key features

Choice
Score
Noul
Multi-question requests
Model catalogue
TypeScript SDK
Idempotency and error handling
Credit billing

Pros and cons

Pros

Pay-as-you-go credits with no subscription and no expiry
Failed calls are not charged
Public model catalogue with prices and limits
Structured outputs with per-option probabilities
Open-source MIT-licensed TypeScript SDK

Cons

Early-stage project: the SDK repository has very few GitHub stars and the company is not identified on the site
No published latency, uptime or accuracy guarantees
Limited to classification, scoring and yes/no style decisions rather than generation
Hosted models are the vendor's own and independent benchmarks are not provided

Pricing

Plans as listed by the vendor on 25 Oct 2026. Check their site for current prices.

See system-one.dev

Starter

$5.99/one-time

5,000 prepaid decision credits.

5,000 credits
Choice and Score and Noul
SDK and playground access
Failed inference refunded

Builder

Scale

$99.99/one-time

120,000 prepaid decision credits.

120,000 credits
Choice and Score and Noul
SDK and playground access
Failed inference refunded

Our ratings

Scored out of 10 by the Finder Atlas editorial team.

7.3overall

API Design: 8.0
Documentation Clarity: 7.8
Pricing Transparency: 8.5
Maturity & Reliability: 5.8
Use Case Breadth: 6.2

Platforms

System One API alternatives

Other tools people compare with System One API.

All 8 alternatives

BrowserbaseFreemium
Cloud browser infrastructure and APIs that let AI agents browse and act on the web
Compare
Browser UseFreemium
Open-source library and cloud platform for AI agents that control real web browsers
Compare
GensparkFreemium
AI super agent workspace that turns one prompt into slides, docs, sheets and research
Compare
ManusFreemium
General AI agent that plans, researches, codes and delivers finished work autonomously
Compare
LindyFree trial
AI teammate that handles email, meetings and recurring work across your team's tools
Compare

Release history

Sep 18, 2026
The public model catalogue lists the Jev model with this release date
The public model catalogue lists the Jev model with this release date.

Reviews

No reviews yet

Used System One API? Help others decide by sharing your experience.

Frequently asked questions

What does the API return?

Structured answers for each question: the selected option with per-option probabilities for Choice, a level for Score, and a probability for Noul.

Does it take actions for me?

No. The site states that model output informs a decision and does not execute a tool or grant permission; your application controls every action.

How is it priced?

Prepaid credits, from $5.99 for 5,000 credits. Cost is questions times 4KB blocks times the model's rate. There is no subscription and credits never expire.

Is there a free allowance?

New accounts get 100 free credits on sign-up, according to the pricing page.

Is the SDK open source?

Yes. @system-one-ai/core is published on npm under the MIT license, with source on GitHub.

Are there uptime or accuracy guarantees?

No. The About and terms pages say no latency, uptime or individual prediction guarantee is published, and recommend evaluating accuracy on your own data.

More Developer Tools tools

View all

DeepSeek

AI Assistants

Free AI chat app and low-cost API running DeepSeek's open-weights V4 models

Freemium

Claude Code

Coding AI

Anthropic's coding agent that edits code and runs commands from terminal, IDE or browser

Paid5.0

Cursor