Tool Pipeline Example

Source: ToolPipelineExample.java

This example demonstrates ToolPipeline: chaining multiple tools into a single compound tool that the LLM calls once. All steps execute sequentially inside a single tool call, with no LLM round-trips between steps.

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Run It

export OPENAI_API_KEY=your-api-key
./gradlew :agentensemble-examples:runToolPipeline

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What It Demonstrates

Two pipelines are built and each is registered as the only tool on a separate task:

Pipeline 1 — extract_and_calculate

Step	Tool	What it does
1	JsonParserTool	Extracts product.base_price from a JSON payload (149.99)
(adapter)	Lambda	Reshapes "149.99" into "149.99 * 1.1"
2	CalculatorTool	Evaluates "149.99 * 1.1" and returns the retail price

The LLM calls extract_and_calculate once with the JSON string. It receives the final numeric result. No LLM inference occurs between steps 1 and 2.

Pipeline 2 — extract_product_name

Step	Tool	What it does
1	JsonParserTool	Extracts the whole product object
(adapter)	Lambda	Prepends "name\n" to produce the path expression for step 2
2	JsonParserTool	Extracts the name field from the product object

This pipeline shows that the same tool type can be chained multiple times, and that adapters reshape the output at each stage.

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Code Walk-through

Build the pipeline

ToolPipeline extractAndCalculate = ToolPipeline.builder()
    .name("extract_and_calculate")
    .description("Given a JSON payload with a 'product.base_price' field, extracts the price "
        + "and returns the price with a 10% markup applied. "
        + "Input: a JSON string containing a product object.")
    .step(new JsonParserTool())
    .adapter(result -> result.getOutput() + " * 1.1")  // (1)
    .step(new CalculatorTool())
    .errorStrategy(PipelineErrorStrategy.FAIL_FAST)    // (2)
    .build();

1. The adapter runs after JsonParserTool succeeds. It takes the extracted price string (e.g., "149.99") and appends the markup formula, producing "149.99 * 1.1" for CalculatorTool.
2. FAIL_FAST (the default) stops the pipeline and returns an error to the LLM if any step fails. The LLM can adapt based on the error message.

Register on a task

var priceTask = Task.builder()
    .description("Use the extract_and_calculate tool to compute the retail price...")
    .expectedOutput("The retail price for Widget Pro with a 10% markup applied.")
    .tools(List.of(extractAndCalculate))  // (1)
    .build();

1. In v2, tools are registered on the task rather than on an explicit agent. The framework synthesizes an agent from the task description and attaches the pipeline to it.

Run the ensemble

EnsembleOutput output = Ensemble.builder()
    .chatLanguageModel(model)
    .task(priceTask)
    .build()
    .run();

The LLM calls extract_and_calculate once with the JSON string. Both steps (JsonParserTool and CalculatorTool) execute inside that single call. The LLM receives one tool result and produces its final answer.

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Sample Output

============================================================
PIPELINE DEMO
============================================================
Input JSON: {"product": {"name": "Widget Pro", "base_price": 149.99, "category": "hardware"}}

--- extract_and_calculate pipeline result ---
The retail price for Widget Pro with a 10% markup applied is $164.99.
Tool calls: 1 | Duration: PT2.341S

--- extract_product_name pipeline result ---
The product name is Widget Pro.
Tool calls: 1 | Duration: PT1.876S

--- Pipeline structure ---
Pipeline: extract_and_calculate
  Error strategy: FAIL_FAST
  Steps (2):
    [1] json_parser
    [2] calculator

Each task made exactly 1 tool call despite involving 2 underlying tool executions. Without a pipeline, the LLM would have needed 2 separate tool calls (and 2 LLM inference round-trips).

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Key Concepts

No LLM round-trips between steps

The LLM calls the pipeline once. All internal steps run as ordinary Java method calls within that single tool invocation. This is the core benefit: deterministic pipelines no longer pay the per-step LLM inference cost.

Adapters bridge format mismatches

The adapter lambda result -> result.getOutput() + " * 1.1" bridges the mismatch between JsonParserTool’s output format and CalculatorTool’s input format. Adapters can contain any logic and can read ToolResult.getStructuredOutput() for typed payloads.

The pipeline is a single tool

From the LLM’s perspective, extract_and_calculate is a regular tool with a name, description, and a single String input. The LLM does not know or need to know that two tools are running inside it.

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Full documentation: Tool Pipeline Guide | Design: Tool Pipeline