Functions

A function is a tool the LLM can call at a node. Its handler does work and returns [result, nextNode]:

• result is delivered to the LLM as the tool result (any JSON value, or null).
• nextNode is the NodeConfig to move to, null to stay on the node and let the LLM respond, or NO_RESPONSE to stay and not respond (the next reply is triggered by the user).

SchemasCopy Anchor Link

The explicit form is a FlowsFunctionSchema, whose handler receives the arguments object and the flow manager. The node example uses it.

Direct functionsCopy Anchor Link

A direct function is a plain async function whose first parameter is flowManager; the other parameters are the tool's arguments, matched by name. JavaScript has no docstrings or type hints at runtime, so attach the description and the parameter schemas as properties:

/**
 * A direct function: the first parameter is the flow manager, the rest are
 * the tool's arguments. Its description and parameter schemas are attached
 * as metadata, since JavaScript has no docstrings or type hints at runtime.
 */
async function bookSlot(fm: FlowManager, day: string, hour: number) {
  fm.state.slot = { day, hour };
  return [{ booked: true }, createAskReasonNode()] as const;
}
Object.assign(bookSlot, {
  description: "Book an appointment slot.",
  parameters: {
    day: { type: "string", description: "Weekday name." },
    hour: { type: "integer", description: "Hour of the day, 0-23." },
  },
});

// Per-tool call options, as a decorator-style wrapper.
const slowLookup = flowsToolOptions({ cancelOnInterruption: false, timeoutSecs: 30 })(
  Object.assign(
    async (fm: FlowManager, query: string) => {
      void fm;
      return [{ matches: [query] }, NO_RESPONSE] as const;
    },
    { description: "Search the records.", parameters: { query: { type: "string" } } },
  ),
);

const node: NodeConfig = {
  taskMessages: [{ role: "developer", content: "Help the caller book a slot." }],
  functions: [bookSlot as any, slowLookup as any],
};

flowsToolOptions sets per-tool cancelOnInterruption (default false in Flows) and timeoutSecs.

Global functionsCopy Anchor Link

Tools available at every node go in globalFunctions on the FlowManager. They are registered once and offered alongside each node's own functions.

ErrorsCopy Anchor Link

If a handler throws, the LLM receives an error result and the conversation stays on the current node. A tool built from a flow config must return [result, TRANSITION_IN_YAML] (the config chooses the destination); returning a node or a node name there is an error reported to the LLM.