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Agents do not receive every imported tool automatically. Tool access is explicit through uses. 
tool fetch_task from mcp.tasks.tool.fetch_task

agent researcher {
    model: model.fast
    uses: [tool.fetch_task]
    instruction: "Fetch task context and summarize it."

    output {
        summary: string
    }
}

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Workflow-owned calls versus model-owned calls

Use a call expression when the workflow author decides exactly which tool to call: 
dynamic {
    task: call tool.fetch_task {
        bindings {
            task_id: input.task_id
        }
    }
}
Use uses when the model may decide whether and how to call the tool during the agent step.

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Guardrails

  • Add input and output schemas to tool declarations when possible.
  • Use bindings for trusted runtime values supplied by the workflow.
  • Keep tool names descriptive and scoped to their purpose.
  • Include only the tools, prompts, and resources an agent needs.