> ## Documentation Index
> Fetch the complete documentation index at: https://docs.ag-ui.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Overview

> Protocol types in the AG-UI .NET SDK

# AGUI.Abstractions

`AGUI.Abstractions` is the protocol-types package for the AG-UI .NET SDK. It
defines the shared event, message, tool, context, capability, interrupt, and
serialization types used by AG-UI clients and servers.

```bash theme={null}
dotnet add package AGUI.Abstractions
```

The package has no opinion about HTTP, ASP.NET Core, or a specific agent
runtime. It is the .NET sibling of `@ag-ui/core`: stable wire types for the
event stream and request payload.

<Note>
  `AGUI.Abstractions` targets `net10.0`, `net9.0`, `net8.0`,
  `netstandard2.0`, and `net472`. It is AOT-compatible: serializable protocol
  types are registered in the source-generated `AGUIJsonSerializerContext`.
</Note>

## SDK packages

The .NET SDK is split into small packages so protocol types, wire formats,
client code, and server code can be adopted independently.

| Package             | Use it for                                                                          |
| ------------------- | ----------------------------------------------------------------------------------- |
| `AGUI.Abstractions` | Protocol events, messages, tools, capabilities, interrupts, and JSON serialization. |
| `AGUI.Formatting`   | Event-stream formatter abstractions and Server-Sent Events support.                 |
| `AGUI.Protobuf`     | Protobuf event-stream formatting and binary protocol support.                       |
| `AGUI.Client`       | HTTP client and `IChatClient` implementation for consuming AG-UI endpoints.         |
| `AGUI.Server`       | Framework-agnostic adapter from `ChatResponseUpdate` streams to AG-UI events.       |

## Wire formats and parity

JSON over Server-Sent Events is the full-fidelity event stream.
`AGUI.Formatting` defines the event-stream formatter contract and SSE support.
`AGUI.Protobuf` adds binary event-stream formatting for the protocol subset
supported by the shared proto schema.

Protocol parity starts in `AGUI.Abstractions`. When the TypeScript reference SDK
adds or changes a wire type, the matching .NET event, message, tool, or
capability type should update alongside `AGUIJsonSerializerContext` and the
compatibility fixtures. Public API tracking files should update whenever a
protocol change adds or changes .NET types.

```bash theme={null}
cd sdks/dotnet
dotnet test tests/AGUI.Abstractions.UnitTests/
dotnet test tests/AGUI.Formatting.UnitTests/
dotnet test tests/AGUI.Protobuf.UnitTests/
```

## Types

Core data structures that represent the building blocks of the protocol:

* [RunAgentInput](/sdk/dotnet/abstractions/types#runagentinput) - Input payload
  for running agents
* [Message types](/sdk/dotnet/abstractions/types#message-types) - Conversation,
  tool, activity, and reasoning messages
* [AGUIContext](/sdk/dotnet/abstractions/types#context) - Contextual information
  provided to agents
* [AGUITool](/sdk/dotnet/abstractions/types#tool) - Tool definitions with JSON
  Schema parameters
* [AgentCapabilities](/sdk/dotnet/abstractions/types#agentcapabilities) -
  Structured capability declarations

<CardGroup cols={2}>
  <Card title="Types Reference" icon="cube" href="/sdk/dotnet/abstractions/types" color="#3B82F6" iconType="solid">
    Complete documentation of the protocol types in `AGUI.Abstractions`
  </Card>

  <Card title="Multimodal Inputs" icon="image" href="/sdk/dotnet/abstractions/multimodal-inputs" color="#3B82F6" iconType="solid">
    User message content parts for text, image, audio, video, document, and binary input
  </Card>
</CardGroup>

## Events

Events power communication between agents and frontends:

* [Lifecycle events](/sdk/dotnet/abstractions/events#lifecycle-events) - Run and
  step tracking
* [Text message events](/sdk/dotnet/abstractions/events#text-message-events) -
  Assistant message streaming
* [Tool call events](/sdk/dotnet/abstractions/events#tool-call-events) -
  Function call lifecycle
* [State management events](/sdk/dotnet/abstractions/events#state-management-events) -
  Agent state and message snapshots
* [Reasoning events](/sdk/dotnet/abstractions/events#reasoning-events) -
  Reasoning stream support
* [Activity events](/sdk/dotnet/abstractions/events#activity-events) -
  Structured progress and transient UI state
* [Special events](/sdk/dotnet/abstractions/events#special-events) - Raw and
  custom events

<Card title="Events Reference" icon="bolt" href="/sdk/dotnet/abstractions/events" color="#3B82F6" iconType="solid">
  Complete documentation of all event types in `AGUI.Abstractions`
</Card>