---
id: strands
title: Strands Agents
sidebar_label: Strands
---

<IntegrationTagsDisplayer otel={true} cicdEvals={true} traceability={true} />

The [Strands Agents SDK](https://strandsagents.com/) is a Python framework for building agents with tools, streaming, and multi-agent patterns.

The `deepeval` integration auto-instruments Strands apps through OpenTelemetry. Every agent invocation, model call, and tool call becomes a span you can inspect, without wiring trace structure by hand.

<AgentTraceTerminal
  title="strands_agent · deepeval"
  ariaLabel="Example Strands agent trace with per-step metric scores"
  lines={[
    { kind: "cmd", name: "deepeval test run test_strands_agent.py" },
    { kind: "blank" },
    { kind: "root", prefix: "●", name: "test_strands_agent" },
    { kind: "blank", prefix: "│" },
    {
      kind: "agent",
      prefix: "└─",
      name: "support_agent",
      metric: "Task Completion",
      score: "0.95",
      duration: "240ms",
      pass: true,
    },
    {
      kind: "llm",
      prefix: "   ├─",
      name: "gpt-4o-mini · plan",
      metric: "G-Eval",
      score: "0.43",
      duration: "96ms",
      pass: false,
    },
    {
      kind: "tool",
      prefix: "   ├─",
      name: 'lookup_order(order_id="A-1001")',
      duration: "52ms",
    },
    {
      kind: "llm",
      prefix: "   └─",
      name: "gpt-4o-mini · respond",
      metric: "Faithfulness",
      score: "0.94",
      duration: "88ms",
      pass: true,
    },
    { kind: "blank" },
    {
      kind: "summary",
      name: "Trace score  0.77   ·   2/3 metrics passed",
      pass: false,
    },
  ]}
/>

`deepeval`'s Strands integration enables you to:

- **Auto-instrument every Strands `Agent` invocation** — each agent call produces a trace, and each agent, LLM, and tool call becomes a component span.
- **Evaluate traces or model / agent components** with any `deepeval` metric.
- **Run evals from scripts or CI/CD** — same metrics, different surfaces.
- **Customize trace and span data at runtime** from tool bodies, wrappers, or staged span config.

:::tip
If you deploy the same Strands agent on [Amazon Bedrock AgentCore](https://aws.amazon.com/bedrock/agentcore/), use the [AgentCore integration](/integrations/frameworks/agentcore) when your outer boundary is the AgentCore app entrypoint. Use **Strands** (`instrument_strands`) when you run Strands directly (scripts, services, notebooks) without the AgentCore runtime wrapper.
:::

## Getting Started

<Steps>

<Step>

### Installation

```bash
pip install -U deepeval strands-agents
```

Under the hood the integration registers an OpenTelemetry span processor that translates Strands spans into `deepeval` traces.

</Step>

<Step>

### Instrument and evaluate

Call `instrument_strands(...)` before creating or invoking your Strands agent. From that point on, Strands spans are available to `deepeval`.

```python title="strands_agent.py" showLineNumbers
import os

from strands import Agent
from strands.models.openai import OpenAIModel

from deepeval.integrations.strands import instrument_strands
from deepeval.dataset import EvaluationDataset, Golden
from deepeval.metrics import TaskCompletionMetric

instrument_strands()

model = OpenAIModel(
    client_args={"api_key": os.environ["OPENAI_API_KEY"]},
    model_id="gpt-4o-mini",
)
agent = Agent(model=model, system_prompt="You are a helpful assistant.")

# Goldens are the inputs you want to evaluate.
dataset = EvaluationDataset(goldens=[Golden(input="Help me return my order.")])

# `evals_iterator` loops through goldens and applies metrics.
for golden in dataset.evals_iterator(metrics=[TaskCompletionMetric()]):
    agent(golden.input)  # Produces trace for evaluation
```

Done ✅. You've run your first eval with full traceability into Strands via `deepeval`.

</Step>

</Steps>

## What gets traced

Each Strands agent invocation produces a **trace** — the end-to-end unit your user observes. Inside that trace are **component spans** for each step the agent took:

- **Agent spans** — Strands agent invocations and agent workflow steps.
- **LLM spans** — model calls emitted through Strands.
- **Tool spans** — tool calls and function executions.

```text
Trace                                    ← what the user observes
└── Agent: support_agent                 ← one Strands agent invocation
    ├── LLM: gpt-4o-mini                 ← component span: model plans
    ├── Tool: lookup_order               ← component span: tool input + output
    └── LLM: gpt-4o-mini                 ← component span: final answer
```

The trace and its component spans are independently evaluable.

## Running evals

There are two surfaces for running evals against a Strands agent. Pick by where you want results to surface — your terminal during development, or your CI pipeline as a pass/fail gate.

### In CI/CD (pytest)

Use the `deepeval` pytest integration. Each parametrized test invocation becomes one agent run; failing metrics fail the test, which fails the build.

```python title="test_strands_agent.py" showLineNumbers
import os

import pytest

from strands import Agent
from strands.models.openai import OpenAIModel

from deepeval import assert_test
from deepeval.dataset import EvaluationDataset, Golden
from deepeval.integrations.strands import instrument_strands
from deepeval.metrics import TaskCompletionMetric

instrument_strands()

model = OpenAIModel(
    client_args={"api_key": os.environ["OPENAI_API_KEY"]},
    model_id="gpt-4o-mini",
)
agent = Agent(model=model)

dataset = EvaluationDataset(goldens=[
    Golden(input="Help me return my order."),
    Golden(input="Explain my refund options."),
])

@pytest.mark.parametrize("golden", dataset.goldens)
def test_strands_agent(golden: Golden):
    agent(golden.input)
    assert_test(golden=golden, metrics=[TaskCompletionMetric()])
```

Run it with:

```bash
deepeval test run test_strands_agent.py
```

### In a script

Use `EvaluationDataset` + `evals_iterator(...)`. Each `Golden` becomes one agent invocation; metrics score the resulting trace.

```python title="strands_agent.py" showLineNumbers
dataset = EvaluationDataset(goldens=[
    Golden(input="Help me return my order."),
    Golden(input="Explain my refund options."),
])

for golden in dataset.evals_iterator(metrics=[TaskCompletionMetric()]):
    agent(golden.input)
```

## Applying metrics to components

The `metrics=[...]` you passed to `evals_iterator` evaluates the **trace**. To evaluate a **component** instead — a specific LLM call or agent span — stage the metric with the appropriate `next_*_span(...)` wrapper before calling the agent.

### Agent spans

```python title="strands_agent.py" showLineNumbers
from deepeval.metrics import TaskCompletionMetric
from deepeval.tracing import next_agent_span
...

def run_strands(prompt: str):
    with next_agent_span(metrics=[TaskCompletionMetric()]):
        return agent(prompt)
```

### LLM calls

```python title="strands_agent.py" showLineNumbers
from deepeval.metrics import AnswerRelevancyMetric
from deepeval.tracing import next_llm_span
...

def run_strands(prompt: str):
    with next_llm_span(metrics=[AnswerRelevancyMetric()]):
        return agent(prompt)
```

For deterministic tool calls, prefer `update_current_span(...)` to add metadata, inputs, and outputs instead of attaching metrics to the tool span.

## Customizing trace and span data at runtime

Trace-level fields you pass to `instrument_strands(...)` are defaults. For anything dynamic, the right API depends on where your code runs.

Strands creates most of the trace structure for you, which means the agent, LLM, and tool spans are mostly hidden behind the app invocation. Calls like `update_current_trace(...)` and `update_current_span(...)` only work while there is an active `deepeval` trace/span in context. In practice, tool bodies are the clearest mutation point, because Strands has already opened the trace and tool span before your function runs.

If you need to customize from outside a tool, use `instrument_strands(...)` for static defaults, `next_*_span(...)` to stage config for the next Strands-created span, or `@observe` / `with trace(...)` when you own the outer operation.

### Trace-level fields from inside a tool

```python title="strands_agent.py" showLineNumbers
from deepeval.tracing import update_current_trace
...

def lookup_order(order_id: str) -> dict:
    order = orders_db.get(order_id)
    update_current_trace(user_id=order["user_id"], metadata={"order_id": order_id})
    return order
```

### Span-level fields from inside a tool

```python title="strands_agent.py" showLineNumbers
from deepeval.tracing import update_current_span
...

def lookup_order(order_id: str) -> dict:
    order = orders_db.get(order_id)
    update_current_span(metadata={"order_id": order_id}, output=order)
    return order
```

## Advanced patterns

The primitives above — `instrument_strands(...)`, `@observe`, `with trace(...)`, `next_*_span(...)`, `update_current_*(...)` — compose around one boundary: Strands owns the auto-instrumented spans, and your code customizes them from the places it can actually see.

### Evaluate subagents with `next_*_span`

`next_*_span(metrics=[...])` stages a metric for the next matching Strands component span. Use this when you want to evaluate a subagent or model step instead of the full trace. Pick the helper that matches the span you want to score: `next_agent_span(...)` or `next_llm_span(...)`.

```python title="strands_agent.py" showLineNumbers
from deepeval.metrics import TaskCompletionMetric
from deepeval.tracing import next_agent_span
...

def run_agent(prompt: str):
    with next_agent_span(metrics=[TaskCompletionMetric()]):
        return agent(prompt)
```

#### No trace-level metrics required

Trace-level metrics are end-to-end metrics: they score the whole trace. They are not strictly necessary here because the `TaskCompletionMetric` is attached to the next agent span, so CI/CD and scripts only need to run the subagent.

This is how you'd run it:

<Tabs items={["CI/CD", "Scripts"]}>
<Tab value="CI/CD">

```python title="test_strands_agent.py" showLineNumbers
import pytest
from deepeval import assert_test
...

@pytest.mark.parametrize("golden", dataset.goldens)
def test_agent_span(golden: Golden):
    run_agent(golden.input)
    assert_test(golden=golden)
```

Then finally:

```bash
deepeval test run test_strands_agent.py
```

</Tab>
<Tab value="Scripts">

```python title="strands_agent.py" showLineNumbers
...

for golden in dataset.evals_iterator():
    run_agent(golden.input)
```

</Tab>
</Tabs>

### Wrap a Strands invocation in `@observe`

When the agent is part of a larger operation, decorate the outer function with `@observe`. Strands spans nest under your observed span automatically.

```python title="strands_agent.py" showLineNumbers
from deepeval.tracing import observe
...

@observe(name="respond_to_user")
def respond_to_user(prompt: str) -> str:
    result = agent(prompt)
    return result.message.get("content", [{}])[0].get("text", "")
```

## API reference

`instrument_strands(...)` accepts the following trace-level kwargs. Each one is a default; runtime calls always win.

| Kwarg               | Type        | Description                                                                |
| ------------------- | ----------- | -------------------------------------------------------------------------- |
| `name`              | `str`       | Default trace name. Override at runtime via `update_current_trace`.        |
| `thread_id`         | `str`       | Default thread identifier. Useful for grouping conversational turns.       |
| `user_id`           | `str`       | Default actor identifier. Override per-request via `update_current_trace`. |
| `metadata`          | `dict`      | Default trace metadata. Merged with runtime overrides; runtime wins.       |
| `tags`              | `list[str]` | Default tags applied to every trace produced by this app.                  |
| `environment`       | `str`       | One of `"development"`, `"staging"`, `"production"`, `"testing"`.          |
| `metric_collection` | `str`       | Default metric collection applied at the trace level.                      |

For runtime helpers (`update_current_trace`, `update_current_span`, `next_agent_span`, `next_llm_span`) and the test-decorator surface (`@observe`, `@assert_test`, `with trace(...)`), see the [tracing reference](/docs/evaluation-llm-tracing).

## FAQs

<FAQs
  qas={[
    {
      question: "Can I evaluate a single Strands subagent rather than the whole run?",
      answer: (
        <>
          Yes. Wrap the call in{" "}
          <code>with next_agent_span(metrics=[...])</code> to stage a metric on
          the next Strands agent span, which scores that subagent on its own.
          For a model step, use <code>next_llm_span(...)</code> instead.
        </>
      ),
    },
    {
      question: "I run Strands in production services — can I keep evaluating there?",
      answer: (
        <>
          Yes. Set <code>environment="production"</code> on{" "}
          <code>instrument_strands(...)</code> and, once logged into Confident
          AI, live traces stream in for{" "}
          <a href="https://www.confident-ai.com/docs/llm-tracing/online-evals">
            online evals
          </a>
          . (If your outer boundary is the AgentCore runtime, use the{" "}
          <a href="/integrations/frameworks/agentcore">AgentCore integration</a>{" "}
          instead.)
        </>
      ),
    },
    {
      question: "Can I run these Strands evals with Pytest?",
      answer: (
        <>
          Yes. Call <code>instrument_strands()</code> before your test, invoke
          the agent inside a parametrized <code>pytest</code> case, and gate the
          build with <code>assert_test(...)</code> plus{" "}
          <code>deepeval test run</code>.
        </>
      ),
    },
    {
      question: "Can I view Strands traces on the cloud?",
      answer: (
        <>
          Yes — optionally. After <code>deepeval login</code>,{" "}
          <a href="https://www.confident-ai.com">Confident AI</a> visualizes the
          same auto-instrumented Strands spans and scores in a shared UI, with
          no extra instrumentation.
        </>
      ),
    },
  ]}
/>
