Update service definition docs

docs/quick-start.mdx

@@ -75,7 +75,7 @@ One such element is the API annotation:
 ```
 
 This annotation is all that's needed for Encore to understand that the Go package `hello` is a service, and
-the `World` function is a public API endpoint. 
+the `World` function is a public API endpoint.
 
 To create more services and endpoints, you simply create new Go packages and define endpoints using
 the `//encore:api` annotation. _If you're curious, you can read more about [defining APIs](/docs/primitives/apis)._
@@ -116,7 +116,7 @@ The Local Development Dashboard is a powerful tool to help you move faster when
 It comes with an API explorer, a Service Catalog with automatically generated documentation, and powerful oberservability features
 like [distributed tracing](/docs/observability/tracing).
 
-Through the Local Development Dashboard you also have access to [Encore Flow](/docs/develop/encore-flow), 
+Through the Local Development Dashboard you also have access to [Encore Flow](/docs/develop/encore-flow),
 a visual representation of your microservice architecture that updates in real-time as you develop your application.
 
 ### Call your API
@@ -289,10 +289,17 @@ interface Response {
 
 As you can see, it's all standard TypeScript.
 
-You define an API endpoint by wrapping a regular async function in a call to `api`. Doing this makes Encore identify the `hello` directory as a service,
-and that the `world` function is a public API endpoint. Encore automatically handles authentication, HTTP routing, request validation, error handling, observability, API documentation, and more.
+You define an API endpoint by wrapping a regular async function in a call to `api`. Doing this makes Encore identify the `world` function as a public API endpoint. Encore automatically handles authentication, HTTP routing, request validation, error handling, observability, API documentation, and more.
 
-If you want to create more services and endpoints, you simply create new folders and define endpoints by wrapping functions in the `api` function. _If you're curious, you can read more about defining [services](/docs/ts/primitives/services) and [APIs](/docs/ts/primitives/apis)._
+The `world` endpoint is part of the `hello` service because in the same folder you will also find a file named `encore.service.ts` which looks like this:
+
+```ts
+import { Service } from "encore.dev/service";
+
+export default new Service("hello");
+```
+
+This is how you create microservices with Encore. Encore will now consider files in the `hello` directory and all its subdirectories as part of the `hello` service. If you want to create more services, simply create a new folders, add a `encore.service.ts` file that is exporting a new `Service`. _If you're curious, you can read more about defining [services](/docs/ts/primitives/services) and [APIs](/docs/ts/primitives/apis)._
 
 The Encore.ts [Backend Framework](/docs/ts) provides several declarative ways of using backend primitives like databases, Pub/Sub, and scheduled tasks by simply writing code.
 
@@ -329,7 +336,7 @@ The Local Development Dashboard is a powerful tool to help you move faster when
 It comes with an API explorer, a Service Catalog with automatically generated documentation, and powerful oberservability features
 like [distributed tracing](/docs/observability/tracing).
 
-Through the Local Development Dashboard you also have access to [Encore Flow](/docs/develop/encore-flow), 
+Through the Local Development Dashboard you also have access to [Encore Flow](/docs/develop/encore-flow),
 a visual representation of your microservice architecture that updates in real-time as you develop your application.
 
 ### Call your API

docs/ts/primitives/services.mdx

@@ -8,7 +8,7 @@ lang: ts
 
 Encore.ts makes it simple to build applications with one or many services, without needing to manually handle the typical complexity of developing microservices.
 
-## Defining services
+## Defining services explicitly (recommended)
 
 To create an Encore service, add a file named `encore.service.ts` in a directory.
 
@@ -25,4 +25,29 @@ export default new Service("my-service");
 
 That's it! Encore will consider this directory and all its subdirectories as part of the service.
 
-For more on how to structure your application, see the [app structure guide](/docs/ts/develop/app-structure).
+For more on how to structure your application, see the [app structure guide](/docs/ts/develop/app-structure).
+
+## Defining services implicitly
+
+If you [define an API](/docs/ts/primitives/services-and-apis#defining-apis), Encore will automatically consider the parent directory as a service. That is, if an `encore.service.ts` file is not present.
+
+On disk it might look like this:
+
+```
+/my-app
+├── encore.app          // ... and other top-level project files
+├── package.json
+│
+├── hello               // hello service (a folder)
+│   └── hello.ts        // contains one or more API endpoints
+│
+└── world               // world service (a folder)
+    └── world.ts        // contains one or more API endpoints
+```
+
+<Callout type="important">
+
+Defining services implicitly limits the way in which you can structure your application as all API endpoints must be defined in the top-level directory for the service.
+  For more flexibility, define services explicitly.
+
+</Callout>

docs/tutorials/rest-api.mdx

@@ -377,9 +377,29 @@ This is needed when you want Encore to manage functionality like secrets and han
 
 Now let's create a new `url` service.
 
-🥐 In your application's root folder, create a new folder `url` and create a new file `url.ts` that looks like this:
+🥐 In your application's root folder, create a directory named `url` containing a file named `encore.service.ts`.
+
+```shell
+$ mkdir url
+$ touch url/encore.service.ts
+```
+
+🥐 Add the following code to `url/encore.service.ts`:
+
+```ts
+-- url/encore.service.ts --
+import { Service } from "encore.dev/service";
+
+export default new Service("url");
+```
+
+This is how you create microservices with Encore. Encore will now consider files in the `url` directory and all its subdirectories as part of the `url` service.
+
+
+🥐 Create a new file `url.ts` in the `url` directory that looks like this:
 
 ```ts
+-- url/url.ts --
 import { api } from "encore.dev/api";
 import { randomBytes } from "node:crypto";
 

docs/tutorials/slack-bot.md

@@ -373,7 +373,25 @@ Since Slack sends custom HTTP headers that we need to pay attention to, we're go
 use a raw endpoint in Encore. For more information on this check out Slack's documentation
 on [Enabling interactivity with Slash Commands](https://api.slack.com/interactivity/slash-commands).
 
-🥐 In your Encore app, create a new directory named `slack` and create a file `slack/slack.ts` with the following contents:
+🥐 In your Encore app, create a directory named `slack` containing a file named `encore.service.ts`.
+
+```shell
+$ mkdir slack
+$ touch slack/encore.service.ts
+```
+
+🥐 Add the following code to `slack/encore.service.ts`:
+
+```ts
+-- slack/encore.service.ts --
+import { Service } from "encore.dev/service";
+
+export default new Service("slack");
+```
+
+This is how you create microservices with Encore. Encore will now consider files in the `slack` directory and all its subdirectories as part of the `slack` service.
+
+🥐 Create a file `slack/slack.ts` with the following contents:
 
 ```ts
 import { api } from "encore.dev/api";

docs/tutorials/uptime.md

@@ -912,13 +912,26 @@ Let's start by creating the functionality to check if a website is currently up
 Later we'll store this result in a database so we can detect when the status changes and
 send alerts.
 
-🥐 Create an Encore service named `monitor` containing a file named `ping.ts`.
+🥐 Create a directory named `monitor` containing a file named `encore.service.ts`.
 
 ```shell
 $ mkdir monitor
-$ touch monitor/ping.ts
+$ touch monitor/encore.service.ts
 ```
 
+🥐 Add the following code to `monitor/encore.service.ts`:
+
+```ts
+-- monitor/encore.service.ts --
+import { Service } from "encore.dev/service";
+
+export default new Service("monitor");
+```
+
+This is how you create microservices with Encore. Encore will now consider files in the `monitor` directory and all its subdirectories as part of the `monitor` service.
+
+🥐 In the `monitor` directory, create a file named `ping.ts`.
+
 🥐 Add an Encore API endpoint named `ping` that takes a URL as input and returns a response
 indicating whether the site is up or down.
 
@@ -1032,13 +1045,25 @@ PASS  Waiting for file changes...
 
 Next, we want to keep track of a list of websites to monitor.
 
-Since most of these APIs will be simple "CRUD" (Create/Read/Update/Delete) endpoints, let's build this service using [Knex.js](https://knexjs.org/), an ORM
-library that makes building CRUD endpoints really simple.
+Since most of these APIs will be simple "CRUD" (Create/Read/Update/Delete) endpoints, let's build this service using [Knex.js](https://knexjs.org/), an ORM library that makes building CRUD endpoints really simple.
 
-🥐 Let's create a new service named `site` with a SQL database. To do so, create a new directory `site` in the application root with `migrations` folder inside that folder:
+🥐 Let's start with creating a new service named `site`:
+
+```shell
+$ mkdir site # Create a new directory in the application root
+$ touch site/encore.service.ts
+```
+
+```ts
+-- site/encore.service.ts --
+import { Service } from "encore.dev/service";
+
+export default new Service("site");
+```
+
+🥐 Now we want to add a SQL database to the `site` service. To do so, create a new directory named `migrations` folder inside the `site` folder:
 
 ```shell
-$ mkdir site
 $ mkdir site/migrations
 ```
 
@@ -1467,7 +1492,21 @@ a Pub/Sub subscriber that posts these events to Slack.
 
 ## 7. Send Slack notifications when a site goes down
 
-🥐 Start by creating a Slack service containing the following:
+🥐 Start by creating a new service named `slack`:
+
+```shell
+$ mkdir slack # Create a new directory in the application root
+$ touch slack/encore.service.ts
+```
+
+```ts
+-- slack/encore.service.ts --
+import { Service } from "encore.dev/service";
+
+export default new Service("slack");
+```
+
+🥐 Add a `slack.ts` file containing the following:
 
 ```ts
 -- slack/slack.ts --