Introduce more fine control over delegation

[bhancockio]

[joaomdmoura]

Disclaimer: This review was made by a crew of AI Agents.

Code Review Comment for PR #2362

Overview

This PR introduces significant enhancements to the agent delegation system in crewAI, allowing for more granular control over which agents can delegate tasks to specific other agents. This represents a shift towards a more structured and efficient delegation strategy.

Key Changes

1. Addition of delegate_to Property in BaseAgent: This allows agents to define which other agents they can delegate tasks to, enhancing control over task routing.
2. Modifications in Delegation Tools Handling: Changes were made to accommodate the new delegation rules, ensuring that the delegation tools reflect the delegate_to configurations.
3. Crew Management Updates: The management of agents has been updated to respect and utilize these new delegation capabilities, improving overall task management.
4. Extensive Test Coverage: Added tests validate the new functionality and ensure consistent behavior across both specific and default delegation scenarios.

Recommendations for Improvement

1. src/crewai/agent.py

• Type Hints Consistency: Ensure that function signatures consistently use type hints. For instance:

  def get_delegation_tools(self, agents: Sequence[BaseAgent]) -> List[BaseTool]:
  

• Documentation: Enhance the documentation to clarify the method's parameters and return types.

2. src/crewai/agents/agent_builder/base_agent.py

• Documentation for delegate_to: The description for the delegate_to property should be explicit about its implications:

  delegate_to: Optional[List["BaseAgent"]] = Field(
      default=None,
      description="List of agents this agent can delegate tasks to. If None and allow_delegation is True, agent can delegate to all available agents.",
  )
  

• Copy Method Validation: Validate the types within delegate_to to ensure all entries are valid BaseAgent instances.

3. src/crewai/crew.py

• Error Handling: Improve the robustness of manager agent creation to ensure only valid instances of BaseAgent are accepted.

  if not isinstance(self.manager_agent, BaseAgent):
      raise TypeError("manager_agent must be an instance of BaseAgent")
  

• Optimize Tools Creation: Refine how delegation tools are constructed, particularly when no specific agents are designated.

4. src/crewai/tools/agent_tools/base_agent_tools.py

• Enhanced Error Handling and Logging: The _execute method should capture and log errors effectively to aid in diagnosing potential issues during delegation.

Additional Recommendations

• Implement validation checks for circular delegation paths to prevent infinite loops.
• Consider adding logging for delegation actions to monitor activity and facilitate debugging.
• Define metrics to gauge delegation patterns across agents, helping to refine future improvements.

Historical Context and Patterns Observed

Historically, changes in the delegation model within crewAI have aimed towards providing more efficient task management. The addition of the delegate_to property signifies continuing evolution towards more sophisticated multi-agent interactions. Related pull requests (PR #2345 and PR #2350) have similarly focused on enhancing delegation capabilities and error handling.

Conclusion

The changes in this PR represent a significant improvement in the agent delegation control system while maintaining code quality and performance benchmarks. By addressing the suggested improvements, the reliability and maintainability of the system will be further enhanced. Continuous attention to documentation and testing will also support ongoing development efforts, ensuring that the delegation capabilities remain robust and user-friendly.

Keep up the great work, and let's make sure to follow up on these recommendations!

[mplachta]

Disclaimer: This review was made by a crew of AI Agents.

Summary of key findings:

This PR introduces significant improvements to CrewAI's agent delegation system by adding a delegate_to property on agents. This property allows agents to specify which other agents they are allowed to delegate tasks to, providing much finer control than the previous approach where delegation was generally allowed to all agents. The changes spread across core agent logic, agent builder base classes, crew execution orchestration, tools handling, and are extensively covered by new unit and integration tests.

Key improvements include:

• Adding delegate_to as an optional list of agents, defaulting to None (meaning delegate to all if delegation is allowed).
• Updating delegation tool gathering methods to respect delegate_to so tools only include agents allowed for delegation.
• Updating crew orchestration to handle delegation restrictions during task execution, especially for hierarchical processes and manager agents.
• Enhancing copying semantics so agent copies properly duplicate the delegate_to list to avoid shared mutable state issues.
• Refining type annotations to use Sequence and List consistently for robustness and interface clarity.
• Defensive attribute checking (via getattr) for optional properties like allow_code_execution and multimodal.
• Removing debug prints accidentally left in production code for cleaner output.
• The test suite includes detailed and well-structured tests covering delegation to all agents, delegation to specific agents, correctness of copied agents, task execution respecting delegation, and delegation tool content correctness.

Specific code improvement suggestions:

1. Simplify get_delegation_tools() in Agent
   The current method uses casting and redundant list() conversions. Simplify by using a single line:

def get_delegation_tools(self, agents: Sequence[BaseAgent]) -> Sequence[BaseTool]:
    agents_to_use = list(self.delegate_to) if self.delegate_to is not None else list(agents)
    return AgentTools(agents=agents_to_use).tools()

2. Remove debug print statements
   For example, this line in execute_task method should be removed:

# print(f"tools: ...")  # Remove before production merge

3. Ensure consistent method signatures with base classes
   In BaseAgent, get_delegation_tools should always return Sequence[BaseTool] and accept Sequence[BaseAgent]. Subclasses must comply for type safety.

4. Defensive attribute access in Crew methods
   Use getattr(agent, "allow_code_execution", False) instead of direct attribute access to prevent runtime errors if agents lack these attributes.

5. Simplify type conversions in Crew
   When preparing tools:

initial_tools = task.tools or agent_to_use.tools or []
prepared_tools = self._prepare_tools(agent_to_use, task, list(initial_tools))

to guarantee consistent list usage downstream.

6. Improve documentation and method docstrings
   Adding or refining docstrings describing expectations for delegate_to and delegation workflow aids maintainability.

Relevant historical context & learnings from PR #2362:

• The delegate_to feature was introduced to give precise task delegation control—this was a major enhancement over previous global delegation permissions (allow_delegation alone).
• Initial patches iterated on method signatures (List vs Sequence), proper copying of delegate_to in agent copies, and expanded tests across agents and crews for this functionality.
• Several fixes removed leftover debug prints and addressed type inconsistencies, improving code quality.
• Extensive new tests validated delegation behavior in various scenarios including hierarchical crew processes and manager agents.

Implications for related files:

• Other agent types or future subclasses must implement get_delegation_tools respecting the new interface.
• Tools leveraging agent lists should accommodate filtered agent lists per delegate_to.
• Crew task orchestration logic relies on delegation restrictions; any addition to crew process flows should consider delegation tool injection.
• Agent copying methods must continue handling delegate_to correctly to avoid shared state bugs.

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Code Review Comment

This PR brings a valuable enhancement by introducing the delegate_to property on agents, enabling controlled delegation to only specified agents rather than defaulting to delegation to all agents. The approach is well-implemented with careful type annotations, proper copying semantics to avoid shared mutable state, and robust integration into the crew orchestration and delegation tool mechanisms.

Notable strengths:

• Clear and consistent use of type hinting with Sequence and List improves code readability and type safety.
• The delegation tools now respect the agent's delegate_to attribute, ensuring only allowed agents appear as delegation targets.
• The manager agent creation correctly sets the delegation list, maintaining expected hierarchical delegation capabilities.
• Tests are comprehensive and well-structured, covering copying behavior, delegation permission enforcement, and tool content validation, significantly raising confidence in the new behavior.

Suggestions for improvement before merging:

• Simplify the get_delegation_tools method in Agent by removing redundant casts and consistently converting sequences to lists upfront, e.g.:

  def get_delegation_tools(self, agents: Sequence[BaseAgent]) -> Sequence[BaseTool]:
      agents_to_use = list(self.delegate_to) if self.delegate_to is not None else list(agents)
      return AgentTools(agents=agents_to_use).tools()
  

• Remove debug print statements left in execute_task (lines printing tool info). These should not appear in production code.
• In crew's tool preparation methods, apply getattr with defaults for optional properties like allow_code_execution and multimodal to avoid attribute errors if agent objects are extended or changed in the future.
• Ensure all abstract method signatures, especially in BaseAgent, match exactly in subclasses with regards to parameter and return types (favor Sequence for flexibility but downcast internally as needed).
• Small docstring enhancements for delegate_to and related delegation methods would improve usability and maintainability.
• Maintain the clear distinction between List and Sequence types across the codebase, using explicit conversions to lists when mutability or list-specific operations are required.

In summary, this PR enhances CrewAI's delegation framework with a thoughtfully designed and well-tested feature for specifying delegation targets per agent. Once minor cleanups and type harmonizations are done, it will be a robust, maintainable addition to the codebase.

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If looking for further background, see the iteration across patches in PR #2362 that show refinement of typing, enforcement of delegation behavior, and expanded testing to ensure correctness and stable integrations.

This detailed review aims to facilitate merging a critical feature that improves collaboration control and task delegation specificity in multi-agent systems managed by CrewAI.

[github-actions[bot]]

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