Skip to main content

Documentation Index

Fetch the complete documentation index at: https://docs.open-harness.dev/llms.txt

Use this file to discover all available pages before exploring further.

By default, all tool calls are allowed. To gate tool execution — for example, prompting a user for confirmation — pass an approve callback to the agent.

​
Basic Approval

const agent = new Agent({
  name: "safe-agent",
  model: openai("gpt-5.4"),
  tools: { ...fsTools, bash },
  approve: async ({ toolName, toolCallId, input }) => {
    // Return true to allow, false to deny
    const answer = await askUser(`Allow ${toolName}?`);
    return answer === "yes";
  },
});

​
ToolCallInfo

The approval callback receives a ToolCallInfo object: 
interface ToolCallInfo {
  toolName: string;
  toolCallId: string;
  input: unknown;
}

​
Denied Tool Calls

When a tool call is denied, a ToolDeniedError is thrown and surfaced to the model as a tool error. This lets the model adjust its approach — for example, by trying a different tool or asking the user for guidance.

​
Async Approval

The callback can be async, enabling a variety of approval patterns:
  • Terminal prompts — ask the user in a CLI
  • Web UI modals — show a confirmation dialog
  • External services — call an approval API or workflow system
// Example: approve reads automatically, require confirmation for writes
const agent = new Agent({
  name: "careful-agent",
  model: openai("gpt-5.4"),
  tools: { ...fsTools, bash },
  approve: async ({ toolName }) => {
    const readOnly = ["readFile", "listFiles", "grep"];
    if (readOnly.includes(toolName)) return true;
    return await promptUser(`Allow ${toolName}?`);
  },
});
Subagents run autonomously without prompting for permission by design. If you need to control subagent tool access, limit the tools you pass to the subagent.