---
title: Model-bound constraints
---

Model-bound constraints let you declare uniqueness rules directly on event types using attributes. No separate constraint class is needed — adorn the event type or its properties with attributes, and Chronicle registers the constraints automatically when the client starts.

Use model-bound constraints when:

- The uniqueness rule applies to a single event type
- You want constraint metadata co-located with the event type it protects
- You want the simplest possible syntax

## Constraint types

| Type | Description |
|---|---|
| [Unique property](/chronicle/constraints/model-bound/unique/) | Enforce that a property value is unique across one or more event types |
| [Unique event type](/chronicle/constraints/model-bound/unique-event-type/) | Enforce that only one event of a specific type can be appended per event source |

## Discovery

Chronicle scans all loaded assemblies for types adorned with `[Unique]` and `[RemoveConstraint]` and registers the constraints with the Kernel automatically when the client starts. No explicit registration is required.