Nested Tool Calls

Use flo.callTool(...) to call another runtime tool from your script.

Generic Form

const result = await flo.callTool({
  tool_id: "some_tool",
  input: { value: 1 },
});

The returned shape is:

• status
• output
• error

Possible statuses are:

• success
• failed
• timeout
• validation_error
• suspended

Typed Built-In Calls

For built-in tools declared in flo.d.ts, TypeScript can infer the input and output shape:

const file = await flo.callTool({
  tool_id: "read_text_file",
  input: {
    path: "task://notes/summary.txt",
    max_bytes: 4096,
  },
});

Error Handling Pattern

Always branch on status instead of assuming output exists:

const result = await flo.callTool({
  tool_id: "read_text_file",
  input: { path: "task://notes/summary.txt" },
});

if (result.status !== "success") {
  return {
    ok: false,
    status: result.status,
    error: result.error,
  };
}

return {
  ok: true,
  content: result.output?.content,
};

Execution Context

Nested tool calls run in the same runtime tool execution context as the calling script. In practice, this means task- and session-scoped helpers continue to operate on the current task and current virtual workspace.

Good uses:

• reading or writing VFS files through built-in tools
• composing smaller tools into a larger workflow
• delegating format-specific work to a built-in tool

Avoid using nested calls as a substitute for simple local code when a direct script implementation is clearer.

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