> ## Documentation Index
> Fetch the complete documentation index at: https://springaicommunity.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# 04 prompts

# Module 04: Prompts

Deep dive into prompt requests and response handling.

## What You'll Learn

* `PromptRequest` structure — session ID and content list
* `PromptResponse` and `StopReason` values
* Content types for prompts

## The Code

`PromptRequest` takes a session ID (from Module 03) and a list of content items. The response includes a `StopReason` that tells you why the agent stopped generating — check this to know if the response is complete, truncated, or refused:

```java theme={null}
// Send a prompt with text content
var response = client.prompt(new PromptRequest(
    session.sessionId(),
    List.of(new TextContent("Explain ACP in one sentence."))
));

System.out.println("Stop reason: " + response.stopReason());
// Output: Stop reason: END_TURN
```

## Stop Reasons

The `StopReason` tells you why the agent finished:

| StopReason   | Description                        |
| ------------ | ---------------------------------- |
| `END_TURN`   | Agent finished responding normally |
| `MAX_TOKENS` | Token limit reached                |
| `REFUSAL`    | Agent refused the request          |
| `CANCELLED`  | Prompt was cancelled by the client |

Understanding stop reasons helps handle different agent behaviors. `END_TURN` is the normal case. `MAX_TOKENS` means the response was truncated. `REFUSAL` may require rephrasing the prompt.

## Source Code

[View on GitHub](https://github.com/markpollack/acp-java-tutorial/tree/main/module-04-prompts)

## Running the Example

```bash theme={null}
export GEMINI_API_KEY=your-key-here
./mvnw exec:java -pl module-04-prompts
```

## Next Module

[Module 05: Streaming Updates](/acp-java-sdk/tutorial/05-streaming-updates) — receive real-time updates during prompt processing.