Tool Chain

# Tool Chain

Explicitly define sequences of tool calls for complex workflows.

## Category
Tool Composition

## Context
Multi-step processes with well-defined order.

## Problem
Agents may not know the correct sequence of tools for complex tasks.

## Solution
Define explicit chains:
- **Step definitions**: Ordered list of tools
- **Data passing**: How outputs feed next inputs
- **Checkpoints**: Where to resume on failure
- **Completion criteria**: When the chain is done

## Example (Python)
```python
# Define a chain for customer onboarding
ONBOARDING_CHAIN = ToolChain(
    name="customer_onboarding",
    steps=[
        Step("create_account", outputs=["account_id"]),
        Step("setup_billing", inputs=["account_id"], outputs=["billing_id"]),
        Step("send_welcome_email", inputs=["account_id"]),
        Step("schedule_kickoff", inputs=["account_id"])
    ]
)

@tool
def run_onboarding(customer_data: CustomerData) -> OnboardingResult:
    """Run the complete customer onboarding chain."""
    return ONBOARDING_CHAIN.execute(customer_data)
```

## Considerations
- Document the chain's purpose and steps
- Handle step failures with compensation or retry
- Allow resuming from checkpoints
- For long running chains, return an execution ID and instructions for how to check the status

## Related Patterns
- task-bundle
- compensation-handler
- dependency-hint

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Source: https://arcade.dev/patterns/tool-chain