Call a tool

Inputs

Operationsstring[]Required

The declared tools to call. Several run in parallel.

Inputmapping

What the tools are called with, keyed by the tool’s own field names. Where absent, the previous step’s value is the input. Input: {} calls with nothing.

AttemptsintegerDefault 1

How many attempts the step may take. A retry calls again only the tools that failed, and keeps the answers that succeeded.

OnExhaustedpolicy

What happens when the attempts run out.Return: <value>Wait

Outputs

<payload>any

With one tool, the tool’s result. With several, an object keyed by operation name: { Field: Pull.Crm } reads one of them.

Example

Operations:
  - Tool: IssueRefund
    Locator: mcp://4b1e9a52-0f3c-4d2a-9e61-2a7f5c3d8b10/issue_refund

Steps:
  - ExecuteTool: Pay
    Operations: [IssueRefund]
    Input:
      invoice: { Field: Read.Invoice }
      amount: { Field: Read.Amount }
    Attempts: 2
    OnExhausted: Wait

The input is checked against the tool’s schema before the call. If every attempt fails, OnExhausted: Wait asks the run’s owner whether to try once more; OnExhausted: { Return: <value> } continues with the value you give instead. Without a policy the step fails.

Tools the model chooses

To let the model pick the calls, follow a ModelCall whose Output is ToolCall with ExecuteModelToolCall, then DeliverResults so the model sees what came back. ExecuteModelToolCall runs only calls its own Operations allow. A call outside them, or one with arguments the tool refuses, is not run; the failure is returned to the model as that call’s result.

- ModelCall: Plan
  Instructions: Look up what the customer is asking about.
  Operations: [Orders, Tickets]
  Output: ToolCall
- ExecuteModelToolCall: Look
  Operations: [Orders, Tickets]
- DeliverResults: HandOver

Related steps

• LoopFor eachCall a tool once per item of a list.Read ›
• ModelAsk the modelLet the model choose the calls.Read ›
• WorkflowRun a workflowCall a whole workflow instead of one tool.Read ›