---
title: "Decision API Use Cases: Routing, Scoring, Judging | System One"
description: "Worked use cases for a typed decision API: tool routing, ranking and scoring, yes/no gating, LLM judging and document extraction, each with the question shape and code you need."
canonical: "https://system-one.dev/en/use-cases"
language: "en"
---

# Decision API Use Cases: Routing, Scoring, Judging | System One

Worked use cases for a typed decision API: tool routing, ranking and scoring, yes/no gating, LLM judging and document extraction, each with the question shape and code you need.

Each page takes one job — routing a request, scoring against a rubric, checking a condition — and shows the question shape, the TypeScript call and where the boundary sits.

- [Turn Screenshots into Typed JSON for Your Agent](https://system-one.dev/en/use-cases/screenshot-to-json): Turn screenshots into typed JSON fields with Clairic's extract(): text, numbers, dates, with confidence and null when a value is missing.
- [Extract Invoice and Receipt Fields with One API Call](https://system-one.dev/en/use-cases/invoice-receipt-extraction): Extract invoice number, dates, totals and tax from invoice text or receipt photos with a typed TypeScript SDK.
- [Judge an AI Answer Before You Show It](https://system-one.dev/en/use-cases/answer-judging): Score an answer against a rubric and check whether it is supported by the source before it reaches a user. Typed verdicts, probabilities you can threshold, and an escalation path for low confidence.
- [Gate a Code Change Before Merge](https://system-one.dev/en/use-cases/code-review-gate): Score a diff's blast radius and ask whether it touches security or data safety, in one request. Typed thresholds let a reviewer or an agent block, flag or wave through a change.
- [Triage a Suspicious Email Before Anyone Clicks](https://system-one.dev/en/use-cases/phishing-triage): Ask one yes/no question about a message's risk and one choice question about handling it, then route on the probability. Low-cost enough to run on every inbound message, not just reported ones.
- [Choose a Game Character's Next Action](https://system-one.dev/en/use-cases/npc-action): Turn a character's state into JSON, ask one choice question over a fixed action list, and get the pick plus a probability for every option. One request replaces a hand-written if-else tree.
- [Moderate a Post Before Publishing](https://system-one.dev/en/use-cases/content-moderation): Ask one yes/no question about whether a post breaks a specific rule, point at the rule text in state, and route on the probability instead of a single label.

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