Add a README for the kits directory

README.md

@@ -8,6 +8,8 @@ Each directory in this repo contains the source code for the extension and a REA
 
 When you find an extension that solves a need for your app or project, all you do is install and configure the extension. With extensions, you don't spend time researching, writing, and debugging the code that implements functionality or automates a task for your app or project.
 
+Several extensions are also available as [Firebase Function Kits](kits) in the [`kits`](kits) directory. A kit is the same functionality packaged as an npm package you add to your own Firebase Functions codebase and deploy yourself, rather than installing it as a managed extension instance.
+
 You can also browse official Firebase extensions from the following sources:
 
 * [Firebase Extensions product page](https://firebase.google.com/products/extensions)

kits/README.md

@@ -0,0 +1,80 @@
+# Firebase Function Kits
+
+This directory contains the source for Firebase Function Kits. A kit is a
+Firebase Extension repackaged as an npm package that you add to your own
+Firebase Functions codebase and deploy into your own project.
+
+While an extension is installed as a managed instance configured through the
+Firebase console or CLI, a kit is code you own: you install the package, export
+the functions you want from your functions entry file, configure it with a
+`.env`, and deploy with `firebase deploy`. There is no hosted version, so the
+functions run in your project, under your service account, on your deployment
+schedule. That also means you can read the source, fork it, or import the
+package's `./lib` entry point and register the triggers yourself.
+
+Each directory here contains the source code for a kit and a README explaining
+how it works, including the roles it needs, the settings it reads, and the
+functions it exports.
+
+## Available kits
+
+| Kit | Description |
+|---|---|
+| [`bigquery-firestore-export`](bigquery-firestore-export) | Reverse-sync rows from BigQuery into Firestore |
+| [`delete-user-data`](delete-user-data) | Delete user data across Firestore, RTDB, and Storage on account deletion |
+| [`firestore-bigquery-export`](firestore-bigquery-export) | Stream a Cloud Firestore collection to BigQuery |
+| [`firestore-bundle-builder`](firestore-bundle-builder) | Build and serve Firestore data bundles |
+| [`firestore-counter`](firestore-counter) | Distributed, sharded counters for Firestore |
+| [`firestore-genai-chatbot`](firestore-genai-chatbot) | Conversational GenAI chatbot backed by Firestore |
+| [`firestore-incremental-capture`](firestore-incremental-capture) | Incremental point-in-time capture of Firestore changes |
+| [`firestore-send-email`](firestore-send-email) | Send emails based on documents written to Firestore |
+| [`firestore-translate-text`](firestore-translate-text) | Translate text written to a Firestore collection |
+| [`firestore-vector-search`](firestore-vector-search) | Vector similarity search over a Firestore collection |
+| [`rtdb-limit-child-nodes`](rtdb-limit-child-nodes) | Limit the number of child nodes under a Realtime Database path |
+| [`speech-to-text`](speech-to-text) | Transcribe Cloud Storage audio with Cloud Speech-to-Text |
+| [`storage-resize-images`](storage-resize-images) | Resize images uploaded to Cloud Storage |
+
+## Using a kit
+
+Kits need Firebase CLI 15.25.1 or later with the `kits` experiment enabled:
+
+```sh
+firebase experiments:enable kits
+```
+
+Install the package into your functions codebase, export the functions you want
+from your entry file, and add a `kit` stanza to `firebase.json` naming the
+instances to deploy:
+
+```json
+{
+  "functions": [
+    {
+      "source": ".",
+      "kit": "firestore-send-email",
+      "instances": {
+        "default": "."
+      }
+    }
+  ]
+}
+```
+
+Each instance ID maps to the directory holding that instance's `.env`, and the
+CLI prefixes every function name with `kit-<instance-id>-`, so one kit can run
+several independently configured instances side by side. See each kit's README
+for its exports, its settings, and the roles the CLI grants on deploy.
+
+## Migrating from an extension
+
+A kit ports the extension's behavior, but it is not a drop-in replacement for
+an installed instance. Deployment still handles the platform setup for you: Firebase
+CLI 15.23.0 or later creates the runtime service account, grants it the roles
+the kit needs, enables the required APIs, and connects any secrets. What moves
+to you is the configuration itself, so check the kit's README against your
+installed instance's settings before deploying, rather than copying the `.env`
+across unchanged.
+
+Extensions themselves are unaffected and remain available. To learn more about
+Firebase Extensions, including how to install them, visit the
+[Firebase documentation](https://firebase.google.com/docs/extensions).