Example: Structured Output

This example shows two approaches to controlling agent output format:

1. Typed output with a Java record — the agent produces JSON that is automatically parsed into a strongly-typed object.
2. Formatted text (Markdown) — the agent produces well-formatted prose using expectedOutput and responseFormat instructions, with no parsing required.

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Example 1: Typed JSON Output

Use outputType when you need the agent’s output as a structured Java object — for downstream processing, serialization, validation, or API responses.

What It Does

1. Researcher produces a structured report (title, list of findings, conclusion)
2. The framework parses the agent’s JSON into a ResearchReport record
3. The caller accesses individual fields via getParsedOutput(ResearchReport.class)

Full Code

import dev.langchain4j.model.openai.OpenAiChatModel;
import net.agentensemble.*;
import net.agentensemble.ensemble.EnsembleOutput;
import net.agentensemble.task.TaskOutput;

import java.util.List;

public class StructuredOutputExample {

    record ResearchReport(String title, List<String> findings, String conclusion) {}

    public static void main(String[] args) {
        var model = OpenAiChatModel.builder()
            .apiKey(System.getenv("OPENAI_API_KEY"))
            .modelName("gpt-4o-mini")
            .build();

        var researcher = Agent.builder()
            .role("Senior Research Analyst")
            .goal("Find accurate, well-structured information on any given topic")
            .llm(model)
            .build();

        var researchTask = Task.builder()
            .description("Research the most important developments in AI agents in 2025")
            .expectedOutput("A structured report with a title, a list of key findings, and a conclusion")
            .agent(researcher)
            .outputType(ResearchReport.class)  // instruct the agent to produce JSON
            .maxOutputRetries(3)               // retry up to 3 times if JSON is invalid (default)
            .build();

        EnsembleOutput output = Ensemble.builder()
            .agent(researcher)
            .task(researchTask)
            .build()
            .run();

        TaskOutput taskOutput = output.getTaskOutputs().get(0);

        // Raw text is always available
        System.out.println("Raw: " + taskOutput.getRaw());

        // Typed access to the parsed object
        ResearchReport report = taskOutput.getParsedOutput(ResearchReport.class);
        System.out.println("Title: " + report.title());
        System.out.println("Findings:");
        report.findings().forEach(f -> System.out.println("  - " + f));
        System.out.println("Conclusion: " + report.conclusion());
    }
}

How It Works

When the task has outputType set:

1. The agent’s user prompt gains an ## Output Format section containing the JSON schema derived from ResearchReport.
2. After the agent produces its response, the framework extracts JSON from the raw text (handling prose, markdown fences, etc.).
3. The JSON is deserialized into ResearchReport using Jackson.
4. If parsing fails, a correction prompt is sent to the agent showing the error and asking it to try again (up to maxOutputRetries times).
5. If all retries are exhausted, OutputParsingException is thrown with the full error history.

Supported Types

Type	Schema Example
String	"string"
int, long, Integer, Long	"integer"
double, float, Double, Float	"number"
boolean, Boolean	"boolean"
List<String>	["string"]
List<MyRecord>	[{...nested schema...}]
Map<String, String>	{"string": "string"}
Enum	"enum: VALUE1, VALUE2"
Nested record/POJO	Inlined nested object

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Example 2: Formatted Markdown Output

Use expectedOutput and Agent.responseFormat when you need well-structured prose (Markdown, bullet points, prose sections) without needing to parse the result into Java objects.

What It Does

1. Researcher produces a research summary in plain text
2. Writer produces a polished Markdown blog post incorporating the research

Full Code

import dev.langchain4j.model.openai.OpenAiChatModel;
import net.agentensemble.*;
import net.agentensemble.ensemble.EnsembleOutput;
import net.agentensemble.task.TaskOutput;
import net.agentensemble.workflow.Workflow;

import java.util.List;
import java.util.Map;

public class MarkdownOutputExample {

    public static void main(String[] args) {
        var model = OpenAiChatModel.builder()
            .apiKey(System.getenv("OPENAI_API_KEY"))
            .modelName("gpt-4o-mini")
            .build();

        // Researcher produces plain-text findings
        var researcher = Agent.builder()
            .role("Senior Research Analyst")
            .goal("Find accurate, well-sourced information on any given topic")
            .llm(model)
            .build();

        // Writer produces Markdown -- responseFormat enforces the format
        var writer = Agent.builder()
            .role("Content Writer")
            .goal("Write engaging, well-structured blog posts from research notes")
            .responseFormat(
                "Always format your response in Markdown. " +
                "Include a title (# heading), an introduction paragraph, " +
                "three sections with subheadings (## heading), and a conclusion.")
            .llm(model)
            .build();

        var researchTask = Task.builder()
            .description("Research the latest developments in {topic}")
            .expectedOutput("A factual summary of key developments, major players, and future outlook")
            .agent(researcher)
            .build();

        var writeTask = Task.builder()
            .description("Write a 700-word blog post about {topic} based on the research provided")
            .expectedOutput(
                "A 700-word blog post in Markdown format with: " +
                "an engaging title, introduction, three sections with subheadings, and a conclusion")
            .agent(writer)
            .context(List.of(researchTask))  // writer receives researcher's output
            .build();

        EnsembleOutput output = Ensemble.builder()
            .agent(researcher)
            .agent(writer)
            .task(researchTask)
            .task(writeTask)
            .workflow(Workflow.SEQUENTIAL)
            .build()
            .run(Map.of("topic", "AI agents in enterprise software"));

        // The final output is the writer's Markdown blog post
        System.out.println(output.getRaw());

        // Access individual task outputs
        for (TaskOutput t : output.getTaskOutputs()) {
            System.out.printf("[%s] completed in %s%n",
                t.getAgentRole(), t.getDuration());
        }
    }
}

Key Points

• responseFormat on Agent appends formatting instructions to the system prompt, guiding the LLM’s output style across all tasks assigned to that agent.
• expectedOutput on Task provides task-specific quality guidance, describing length, structure, and content requirements.
• The raw field of TaskOutput always contains the complete agent response as a string.

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Running the Example

git clone https://github.com/AgentEnsemble/agentensemble.git
cd agentensemble
export OPENAI_API_KEY=your-api-key

# Default topic (AI agents in 2025)
./gradlew :agentensemble-examples:runStructuredOutput

# Custom topic
./gradlew :agentensemble-examples:runStructuredOutput --args="quantum computing"

The example runs both Part 1 (typed JSON output) and Part 2 (formatted Markdown output) for the same topic in a single execution so you can compare the two approaches side by side.

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Combining Both Approaches

You can mix structured and plain-text tasks in the same ensemble:

// Task 1: structured output -- the researcher produces a parsed Java object
var researchTask = Task.builder()
    .description("Research AI trends")
    .expectedOutput("A structured report")
    .agent(researcher)
    .outputType(ResearchReport.class)
    .build();

// Task 2: Markdown output -- the writer uses the research to produce prose
var writeTask = Task.builder()
    .description("Write a blog post based on the research")
    .expectedOutput("A 700-word blog post in Markdown")
    .agent(writer)
    .context(List.of(researchTask))  // receives the raw JSON as context
    // no outputType -- plain text result
    .build();

EnsembleOutput output = Ensemble.builder()
    .agent(researcher).agent(writer)
    .task(researchTask).task(writeTask)
    .build()
    .run();

// Access the structured output from task 1
ResearchReport report = output.getTaskOutputs().get(0).getParsedOutput(ResearchReport.class);

// Access the Markdown from task 2
String blogPost = output.getTaskOutputs().get(1).getRaw();