magnus919_agent-skills/crewai/references/tool-integration.md

CrewAI Tool Integration

@tool Decorator

from crewai.tools import tool

@tool("search_web")
def search_web(query: str) -> str:
    """Search the web for current information."""
    return f"Results for: {query}"

@tool("calculate")
def calculate(expression: str) -> str:
    """Evaluate a mathematical expression."""
    return str(eval(expression))

Assigning Tools

Tools are assigned to agents:

agent = Agent(
    role="Researcher",
    goal="Find information",
    backstory="Expert researcher",
    tools=[search_web, calculate],  # Agent-level tools
)

# Or task-level (overrides agent tools)
task = Task(
    description="Research and compute",
    agent=agent,
    tools=[search_web],  # Task-specific — only this tool is available
)

Built-in Tools

CrewAI ships tool packages: crewai-tools with SerperDevTool, ScrapeWebsiteTool, etc. Install separately:

pip install crewai-tools

Tool Design Guidelines

• Docstring matters. The docstring/description is what the LLM sees to decide when to use the tool.
• Type hints required. Tool parameters use type hints for schema generation.
• Handle errors gracefully. Tool failures mark tasks as failed but don't raise exceptions.
• Return strings. Keep return values as strings for consistent handling.
• Cache results. Same input → same cached output (controlled by cache parameter).