Tool Calling - Superwire

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
    }
}

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.

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.