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

# Execution Behavior

> Validate agent execution flow, tool usage, and sequence of operations

Execution behavior validation ensures your agent follows the expected workflow. Verify tool selection, parameter values, execution order, and sequence compliance using flow validators.

## Example

This example demonstrates how to validate complex execution flows with parallel tool execution and sequential processing using nested `seq!` and `parallel!` validators.

### Eval Configuration

```yaml evals.yaml theme={"dark"}
- name: eval_travel_assistant_workflow
  description: Fetch data in parallel then processes sequentially
  runnable: agent.py::agent
  params:
    prompt: "I'm planning a trip to Madrid. What's the current time, the weather forecast, and flight prices?"
  seq!:
    - llm
    - parallel!:
        - get_datetime:
            input:
              timezone:
                eq!: "Europe/Madrid"
        - get_weather:
            input:
              city:
                eq!: "Madrid"
    - search_flights:
        input:
          destination:
            contains!: "Madrid"
    - llm
```

### Agent Implementation

```python agent.py theme={"dark"}
from timbal import Agent

async def get_datetime(timezone: str) -> str:
    """Get current datetime for a timezone."""
    return f"2024-01-15 14:30:00 {timezone}"

async def get_weather(city: str) -> str:
    """Get weather forecast for a city."""
    weather_data = {
        "Madrid": "Sunny, 18°C",
        "Barcelona": "Cloudy, 15°C"
    }
    return weather_data.get(city, "Weather data unavailable")

async def search_flights(destination: str) -> str:
    """Search for flights to a destination."""
    return f"Found flights to {destination}"

agent = Agent(
    name="travel_assistant",
    model="openai/gpt-5.2",
    tools=[get_datetime, get_weather, search_flights],
)
```

### Running Evaluations

```bash theme={"dark"}
python -m timbal.evals.cli evals.yaml
```

## How It Works

1. **Initial Processing**: The agent starts with an LLM call to understand the request.

2. **Parallel Execution**: Two tools (`get_datetime` and `get_weather`) execute in parallel using `parallel!`, improving efficiency by fetching independent data simultaneously.

3. **Sequential Processing**: After parallel execution completes, `search_flights` runs sequentially, as it may depend on the previous results.

4. **Final Processing**: A final LLM call synthesizes all the gathered information into a response.

5. **Validation**: The `seq!` validator ensures:
   * Tools execute in the correct order
   * Parallel tools run simultaneously (overlapping execution times)
   * Tool inputs match expected values using nested validators

## Evaluation Results

### Successful Validation

When the agent follows the expected workflow with parallel and sequential execution:

```
──────────────────── Timbal Evals ────────────────────
collected 1 evals from 1 file

 PASSED  evals.yaml::eval_travel_assistant_workflow [4.65s]
└── travel_assistant
    └── ✓ seq!
        ├── llm
        ├── ✓ parallel!
        │   ├── get_datetime
        │   │   └── ✓ input.timezone.eq! ("Europe/Madrid")
        │   └── get_weather
        │       └── ✓ input.city.eq! ("Madrid")
        ├── search_flights
        │   └── ✓ input.destination.contains! ("Madrid")
        └── llm

============================= 1 passed in 4.65s ==============================
```

### Failed Validation

When the agent doesn't follow the expected execution pattern:

```
──────────────────── Timbal Evals ────────────────────
collected 1 evals from 1 file

 FAILED  evals.yaml::eval_travel_assistant_workflow [4.36s]
└── travel_assistant
    └── ✗ seq!
        ├── llm
        ├── ✗ parallel!
        │   ├── get_datetime
        │   │   └── ✓ input.timezone.eq! ("Europe/Madrid")
        │   └── get_weather
        │       └── ✓ input.city.eq! ("Madrid")
        ├── search_flights
        │   └── ✓ input.destination.contains! ("Madrid")
        └── llm

!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 1 failed in 4.36s !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
```

## Key Features

* **Nested Flow Validation**: Combine `seq!` and `parallel!` to validate complex execution patterns
* **Parallel Execution**: Use `parallel!` to ensure independent tools run simultaneously for better performance
* **Sequential Processing**: Use `seq!` to enforce order when tools depend on previous results
* **Tool Input Validation**: Validate tool input parameters using nested validators within flow validators
* **Span Validation**: Validate individual span properties (input, output, elapsed, usage) within sequences
* **Workflow Compliance**: Ensure agents follow expected execution patterns and optimize tool usage