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Sub-agents let one Duckie run invoke another active agent as a child run. Use a sub-agent when a specialized agent should handle part of a conversation while the parent agent or workflow keeps ownership of the overall process. The child agent follows its own start mode and configured access to resources, tools, guidelines, and guardrails.

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When to Use Sub-Agents

Sub-agents are useful when:
Use caseExample
Specialized expertiseA general support agent delegates billing questions to a Billing Agent
Reusable workflowsSeveral parent workflows call the same Refund Specialist Agent
Safer tool accessOnly a dedicated agent can use sensitive account or billing tools
Clear handoffsA triage agent gathers context, then delegates a narrow task to another agent

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How Agents Can Invoke Sub-Agents

Duckie supports sub-agent calls from autonomous agents and workflows.

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From an Autonomous Agent

An autonomous agent can call other agents as tools when those agents are enabled in Callable agents. To configure this:
  1. Open Build > Agents.
  2. Open the autonomous agent that will call other agents.
  3. In Callable agents, choose None, All, or specific agents.
  4. Save the agent.
When the autonomous agent runs, each callable active agent is described to it by name and description. The calling agent decides when to delegate, sends a task, and chooses whether to include the current conversation history.
Agent descriptions matter for delegation. The calling agent uses the target agent’s name and description to decide which sub-agent is appropriate.

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From a Workflow

Workflows can invoke an agent from a Tool node by selecting an agent in the Agents tab. To add an Agent action:
  1. Open a workflow in the builder.
  2. Add a Tool node.
  3. Open the tool selector and choose Agents.
  4. Select an active agent.
  5. Configure the Agent action inputs.
The selected agent can start autonomously, from a workflow, or from a runbook. Duckie routes the child run based on that agent’s start mode.

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Child Agent Inputs

Every child agent run must receive at least one of:
  • Instructions - the task or instruction for the child agent
  • Conversation history - the parent run’s customer-visible messages
Workflows can also pass Additional context.
Input combinationWhat the child receives
Instructions onlyThe delegated instructions become the child run’s message
Conversation history and instructionsThe parent conversation is copied first, then the delegated instructions are appended
Conversation history onlyThe copied parent conversation becomes the child run input
Autonomous agent calls always include a task and a required conversation-history choice. Workflow Agent actions can use any valid combination.

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Conversation History

Use conversation history when the child agent needs prior customer messages to complete the task. Workflow Agent actions include conversation history by default. Turn conversation history off when the delegated instructions contain all required context and the child agent should not reason over the full parent conversation.

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Additional Context

Additional context is available on workflow Agent actions. It is a list, so you can pass more than one context item. Use additional context for structured handoff details such as:
  • An order lookup result
  • A policy excerpt
  • A customer segment or plan
  • A value generated by an earlier workflow node
Duckie adds additional context to the child run metadata under additional_context. Child runs also inherit the parent run metadata.
Do not pass secrets, credentials, API keys, tokens, or similar values as additional context.

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What the Parent Receives

The parent receives a compact result from the child run. The child run’s full transcript and steps stay available on the child run.
CallerParent-facing output
Autonomous agentA tool result with success, child_run_id, status, and compact_result
Workflow Agent actionA node output with status, resolutionSummary, resolutionType, subRunId, agentId, startWithType, and waitingForInput when relevant
For autonomous child agents, the child returns its internal result with Send result to calling agent. That result becomes the parent-facing summary. This is separate from responder tools.

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Customer-Visible Responses

Responder tools still send customer-visible messages. If a child agent uses a responder, Duckie also copies the child-authored response into the parent run messages so the parent run transcript stays complete. Use Send result to calling agent for internal parent-facing output. Use a responder only when the child agent should send a customer-visible response.

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Best Practices

  • Give each sub-agent a clear job boundary.
  • Keep agent names and descriptions specific enough for another agent to choose correctly.
  • Pass focused instructions, even when including conversation history.
  • Include conversation history only when the child needs it.
  • Use additional context as a short list of relevant facts, not as a dump of every previous node output.
  • Test parent and child behavior together in the playground.

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Next Steps

Autonomous Agents

Configure agents that can delegate work at run time

Creating Workflows

Add Agent actions to deterministic workflows

Agent Configuration

Review agent settings and access control

Playground

Test sub-agent handoffs before deployment