Adds more details to the type guide

web/docs/guides/api/generating-types.mdx

@@ -4,10 +4,56 @@ title: "Generating Types"
 description: How to generate types for your API and Supabase libraries.
 ---
 
+Supabase APIs are generated from your database, which means that we can use database introspection to generate type-safe API definitions.
+
+### Generating types from OpenAPI specification
+
+Supabase generates an OpenAPI specification file for your database which can be used to generate your data types for usage with TypeScript.
+
+The OpenAPI specification for your Supabase project can be accessed as follows:
+
+```txt
+https://your-project.supabase.co/rest/v1/?apikey=your-anon-key
+```
+
+Using the open source [openapi-typescript](https://github.com/drwpow/openapi-typescript#%EF%B8%8F-reading-specs-from-remote-resource) tool you can generate your types and store them locally:
+
+```bash
+npx openapi-typescript https://your-project.supabase.co/rest/v1/?apikey=your-anon-key --output types/supabase.ts
+```
+
+Important notes:
+
+- Since the generator uses JSON API, there is no way to determine if a column is an Array. It will generate array types as `string`, even though Supabase handles this automatically and returns arrays.
+  You can fix this manually in the files by changing the type, e.g. `names: string` -> `names: string[]`
+- The types won't automatically stay in sync with your database, so make sure to regenerate your types after your make changes to your database.
+
+After you have generated your types, you can use them in your TypeScript projects:
+
+```ts
+import { NextApiRequest, NextApiResponse } from "next";
+import { createClient } from "@supabase/supabase-js";
+import { definitions } from "../../types/supabase";
+
+const supabase = createClient(
+  process.env.NEXT_PUBLIC_SUPABASE_URL,
+  process.env.SUPABASE_SECRET_KEY
+);
+
+export default async (req: NextApiRequest, res: NextApiResponse) => {
+  const allOnlineUsers = await supabase
+    .from<definitions["users"]>("users")
+    .select("*")
+    .eq("status", "ONLINE");
+  res.status(200).json(allOnlineUsers);
+};
+```
+
+For more advance type-support, check out [`postgrest-js-tools`](https://github.com/mzalevski/postgrest-js-tools).
+
 ## Update types automatically with GitHub Actions
 
 One way to keep your type definitions in sync with your database is to set up a GitHub action that runs on a schedule.
-Supabase offers a Swagger OpenAPI specification for the REST data endpoint which you can use to generate definitions.
 
 The following script can be run in your terminal to produce the file `types/database/index.ts`.
 ```
@@ -20,7 +66,8 @@ You can add this script to your `package.json` and run it using `npm run update-
 "update-types": "npx openapi-typescript \"${SUPABASE_URL}/rest/v1/?apikey=${SUPABASE_ANON_KEY}\" --version=2 --output types/database/index.ts"
 ```
 
-You can use GitHub actions to generate this file automatically. Create a file `.github/workflows/update-types.yml` and add the following snippet into this file to define the action along with the environment variables. If there is a change to your definitions, this script will commit the change to your repo.
+You can use GitHub actions to generate this file automatically. This script will commit the change to your repo every night.
+Create a file `.github/workflows/update-types.yml` and add the following snippet into this file to define the action along with the environment variables. 
 
 ```yml
 name: Update database types
@@ -68,4 +115,4 @@ Alternatively, you can use a community-supported GitHub action: [generate-supaba
 
 ## Resources
 
-- [How to create and test a GitHub Action that generates Supabase database types](https://blog.esteetey.dev/how-to-create-and-test-a-github-action-that-generates-types-from-supabase-database)
+- [Generating Supabase types with GitHub Actions](https://blog.esteetey.dev/how-to-create-and-test-a-github-action-that-generates-types-from-supabase-database)