# Analyze your first API

At the end of this tutorial, Faustine has a list of the operations of the Nimbus CRM backend that you have reviewed, and one of them has returned real data from your running server.

Nimbus CRM is the example app of these docs: a CRM with contacts, companies, deals, tasks and invoices. Its backend is an Express app with a REST API under `/api`. The code is at [github.com/faustine-ai/example-nimbus-crm](https://github.com/faustine-ai/example-nimbus-crm).

In this tutorial, you:

- [Create the API](#create-the-api)
- [Run the analysis](#run-the-analysis)
- [Review the operations](#review-the-operations)
- [Add a connection](#add-a-connection)
- [Test an operation](#test-an-operation)

## Before you begin

- A model provider connected to your workspace. See [Connect your model provider](https://docs.faustine.ai/get-started/connect-your-ai-provider/).
- A fork of `faustine-ai/example-nimbus-crm` in a GitHub account that Faustine can read. See [Connect GitHub](https://docs.faustine.ai/technologies/github/).
- Nimbus CRM running at a URL that Faustine can reach over the internet. A server on `localhost` is not reachable. The repository's `app/README.md` has the command for the single-container build, which serves the API on port 4000.

## Create the API

1. In the portal, go to [**APIs**](https://auth.faustine.ai/go?to=%2Fintegrations%2Fapis) and select **New API**.
2. In **API type**, select **REST**.
3. In **Architecture**, select **One service**, then **Continue**.
4. In **Language & framework**, select **Express**.
5. In **Details**, enter `Nimbus CRM` in **Name**. The wizard fills **Namespace** with `nimbuscrm`. Select **Continue**.
6. In **Connect your code**, select GitHub, then your fork in **Repository**. Select `main` in **Branch**.
7. In **API path**, enter `app/backend`. The repository also contains the front end, and the API is in this folder.
8. Select **Continue**.
9. In **Spec (optional)**, select **Skip**. Nimbus CRM has no OpenAPI file, so the analysis reads the routes from the code.
10. In **Keep the API up to date**, leave **Automatic** selected and select **Continue**.
11. In **Review & analyze**, select **Create & start analysis**.

The namespace is the first part of every operation key, such as `nimbuscrm.contacts.list`. It cannot be changed later.

## Run the analysis

The portal opens the analysis page. The run clones the repository, discovers the operations and how a client authenticates, and proposes a kind and a confirmation flag for each operation. You can leave the page while it runs.

> **Checkpoint:** The status reads **Analysis complete**. Under it, the page shows the number of operations with the split between read and write, how many need confirmation, and the sign-in that was detected.

Select **Open the API page**.

![The analysis page after the run, with the operation counts and the detected sign-in.](https://docs.faustine.ai/images/apis/analysis-light.png)

## Review the operations

The **Overview** tab shows **Set up this API** with three steps. **Analyze the API** is done. **Add a connection** and **Serve it from a gateway** are pending.

1. Select the **Operations** tab. The operations are grouped by resource: `/contacts`, `/companies`, `/deals` and the others.
2. Select the row of the operation that lists contacts. It unfolds to show its **Endpoint**, `GET /api/contacts`, its kind and its description.
3. Select **Schema** in the same row. The **Request** tab shows the input the operation accepts. Close the dialog.
4. Check the **Kind** column of the group. Operations that create, update or delete are `write`. To change a kind, select the pencil next to its badge.
5. Check the **Requires confirmation** column. Turn the switch on for each delete operation where it is off.
6. If you changed anything, select **Save changes**.
7. Under the table, open **Hidden (auth endpoints)**. The login route is listed there. Faustine uses it to sign in and does not expose it to agents.

Go back to the **Overview** tab. If **To review** has a row about operations that require confirmation, select **Looks right**.

## Add a connection

A connection tells Faustine where the backend runs and which credential to use. This tutorial covers the minimum. For every field, see [Add a connection](https://docs.faustine.ai/apis/add-a-connection/).

1. Select the **Connections** tab, then **New connection**.
2. In **Endpoint**, enter `Staging` in **Name**. In **Base URL**, enter the origin of your server, such as `https://nimbus.example.com`, without `/api`. The operation paths already start with `/api`.
3. In **Credentials**, enter the values the step asks for. They depend on the sign-in in the API's **Authentication** tab. For a sign-in through the login route, enter the seeded account from the Nimbus CRM README: `admin@crm.test` and `admin123`.
4. Skip **Labels**.
5. In **Test**, select the operation that lists contacts in **Operation**, then run the test.
6. In **Review & create**, select **Create connection**.

If the **Credentials** step reports that the sign-in is not set, open the **Authentication** tab first. See [Authentication](https://docs.faustine.ai/apis/authentication/).

> **Checkpoint:** The **Connections** tab lists **Staging**. In the **Overview** tab, **Add a connection** is done.

## Test an operation

1. Select the **Operations** tab.
2. In the row of the operation that lists contacts, select **Test**.
3. In **Connection**, select **Staging**.
4. Replace the content of **Input** with `{}`. The operation has no required input, and its optional `search` and `status` fields filter the list.
5. Select **Run test**, then confirm with **Run test**.

> **Checkpoint:** **Result** shows `200 OK` and a JSON array with the seeded contacts of your Nimbus CRM instance.

Repeat the test for the other read operations you plan to serve. A test of a write operation creates or changes records on your server.

## What you built

Your workspace has an API named Nimbus CRM with reviewed operations and a connection to your server. It is listed under [**APIs**](https://auth.faustine.ai/go?to=%2Fintegrations%2Fapis), and it updates when you push to the fork.

## Next steps

- [Write your first recipe](https://docs.faustine.ai/apis/write-your-first-recipe/): add an operation that creates a company and its first contact in one call.
- [Add an API to a gateway](https://docs.faustine.ai/agent-gateway/add-an-api/): serve these operations to AI clients.
- [Generate and run API tests](https://docs.faustine.ai/apis/tests/): test every operation in one run.
- [The analysis](https://docs.faustine.ai/apis/analysis/): what the run read and what you can re-run.