createCallTracker

Creates a counter for a tool's calls, so its unregistration can wait for them.

Creates a counter for a tool’s calls, so its unregistration can wait for them. Pair it with deferRelease and pass it as calls to registerWebTool; the registry and useWebTool already do, so you reach for it only when you register tools yourself.

Import

import { createCallTracker } from "@webmcp-agents/core";
import type { CallTracker } from "@webmcp-agents/core";

Example

Count the calls of one registration, and ask whether it is safe to unregister it. deferRelease does the waiting for you.

import {
  createCallTracker,
  defineWebTool,
  registerWebTool,
} from "@webmcp-agents/core";

const tool = defineWebTool({
  id: "get_time",
  description: "Read the time.",
  readOnly: true,
  execute: () => new Date().toISOString(),
});

// registerWebTool counts each call of the tool on this tracker.
const calls = createCallTracker();
export const unregister = registerWebTool(tool, { calls });

// You can count your own work on it too.
export async function refresh(load: () => Promise<void>) {
  await calls.track(load);
}

// While a call runs, and for 500 ms after the last one settled.
export const canUnregister = () => !calls.busy();

Options

None: createCallTracker() takes no arguments.

Returns

A CallTracker:

Name	Type	Description
`track(call)`	`<T>(call: () => T \| Promise<T>) => Promise<T>`	Run one call and count it until it settles. Resolves or rejects with the call’s own outcome.
`busy()`	`() => boolean`	`true` while a call runs, and for `RESPONSE_GRACE_MS` (500 ms) after the last one settled.

Notes

The grace after the last call gives the browser time to deliver the answer before the tool changes.
busy is a plain function and can be passed as isBusy without binding.
A rejected call still counts as settled: the counter drops in a finally.
Each tool needs its own tracker: it counts calls, not which tool they were for.