Tool Approvals (Human-in-the-Loop)

Some tool calls need a human to confirm inputs before they execute—think payments, deployments, or data export. This page explains how to integrate human-in-the-loop approvals with the Smart Agent runtime.

Enabling approvals on a tool

Set needsApproval: true when creating a tool. Optionally include UI hints:

const deploy = createTool({
  name: "deploy_service",
  description: "Roll out the current build to production",
  schema: z.object({ version: z.string() }),
  needsApproval: true,
  approvalPrompt: "Send build {{version}} to prod?",
  approvalDefaults: { channel: "ops", priority: "high" },
  async func({ version }) {
    return rollout(version);
  },
});

Once selected by the model, the agent will:

1. Append a pendingApprovals entry to the state.
2. Emit a tool_approval event with status: "pending".
3. Pause execution until the approval is resolved.

Inspecting pendingApprovals

Each entry contains all the data you need to render a review form:

{
  id: "approve_deploy_1",
  createdAt: "2025-10-08T11:24:33.120Z",
  toolName: "deploy_service",
  toolCallId: "call_abc",
  args: { version: "1.4.2" },
  metadata: {
    prompt: "Send build 1.4.2 to prod?",
    defaults: { channel: "ops", priority: "high" }
  }
}

You can serialize the whole state (using agent.snapshot) and surface the approval queue in your app or dashboard.

Resolving an approval

Call agent.resolveToolApproval with the original state and the decision:

const decision = await agent.resolveToolApproval(state, {
  id: pending.id,
  approved: true,
  decidedBy: "on-call",
  comment: "Go for it",
  approvedArgs: { ...pending.args, dryRun: false },
});

const resumed = await agent.invoke(decision);

• approved: true – the tool executes immediately on the next turn.
• approved: false – the tool is skipped; the agent receives a rejection message.
• approvedArgs (optional) – override arguments before execution.

Coordinating with onStateChange

Pair approvals with onStateChange checkpoints to pause at the right moment:

const result = await agent.invoke(state, {
  onStateChange(current) {
    if (current.ctx?.__awaitingApproval) return true; // capture snapshot
    return false;
  },
  checkpointReason: "awaiting-human-approval",
});

This ensures the run returns immediately after the approval is queued, letting you persist the checkpoint and resume once a reviewer acts.

Event stream integration

Approvals emit structured events you can feed into telemetry pipelines:

• status: "pending" – tool call is waiting for review.
• status: "approved" – reviewer green-lit the call.
• status: "rejected" – reviewer blocked the call.

Inside the event payload you’ll find toolName, toolCallId, and the id you need to resolve the approval later.

Recommended UX flow

1. Detect pause – onStateChange or direct state inspection shows ctx.__awaitingApproval.
2. Display review card – render toolName, arguments, prompt, and metadata.
3. Collect decision – allow reviewers to tweak arguments or annotate decisions.
4. Resolve + resume – call resolveToolApproval; optionally re-run with agent.resume if you persisted a snapshot.

Need a full working example? Check examples/tool-approval/tool-approval.ts for end-to-end wiring.

For deeper internals, see the Tool Development guide. To combine approvals with checkpoints and resumable runs, continue with State Management.