This blogpost will help you to explore and interact with MS graph API endpoint’s using the following tools

• Postman client
  • Signed in as a user/On-behalf-of API call (Delegated permission)
  • Application/daemon API call (Application permissions)
• Graph Explorer

I have used MS graph extensively on different MS cloud services like SharePoint, PowerAutomate, PowerApps, Azure services like Azure functions and on devices like Raspberry Pi. It is a very powerful service in Microsoft 365 platform. Let start with some basics

Introduction:

MS Graph API is a RESTful web API which enables you to access different Microsoft 365 cloud service resources through its unified programmability model.

Microsoft Graph exposes REST APIs and client libraries to access data on the following Microsoft cloud services:

• Microsoft 365 services: Delve, Excel, Microsoft Bookings, Microsoft Teams, OneDrive, OneNote, Outlook/Exchange, Planner, SharePoint, Workplace Analytics.
• Enterprise Mobility and Security services: Advanced Threat Analytics, Advanced Threat Protection, Azure Active Directory, Identity Manager, and Intune.
• Windows 10 services: activities, devices, notifications, Universal Print (preview).
• Dynamics 365 Business Central.

Permission Types:

MS Graph exposes granular permissions that controls the access of the apps that has to the different resources like sites, users, groups etc. There are two types of permission

• Delegated permissions are used by apps that have a signed-in user present. For these apps, either the user or an administrator consents to the permissions that the app requests and the app can act as the signed-in user when making calls to Microsoft Graph.
• Application permissions are used by apps that run without a signed-in user present. For e.g Apps that run as background services or daemons. Application permissions can only be consented by an administrator.

Access token:

To call a MS Graph API all you need is an access token in the authorization header of an HTTP request.

GET https://graph.microsoft.com/v1.0/me/ HTTP/1.1

Host: graph.microsoft.com

Authorization: Bearer EwAoA8l6BAAU … 7PqHGsykYj7A0XqHCjbKKgWSkcAg==

The access tokens are issued by the Microsoft identity platform which contains information to validate if the requestor has appropriate permissions to perform the operation they are requesting. An active directory app is a pre-requisite to generate an access token to call a Graph API endpoint.

There are also Microsoft identity platform authentication libraries for .NET, JS Android, Objective-C, Python, Java, Angular facilitating validation, cookie handling, token caching and on maintaining a secure connection. Let’s now go ahead and see the tools

MS Graph Explorer:

Graph explorer is a web-based tool which can be used to build and test requests using Microsoft Graph API. The explorer can be accessed from the following URL:

https://developer.microsoft.com/en-us/graph/graph-explorer

There will be a default Active directory application on the Organizational Active directory of the M365 tenant by the name Graph Explorer with application id de8bc8b5-d9f9-48b1-a8ad-b748da725064. This app can be accessed from the Enterprise applications blade of the Active directory as shown below

Delegated permissions are used by Graph Explorer. Based on your access role & admin consent’s you would be able to call different Microsoft Graph API from this tool. After you have signed into the Graph Explorer tool, the access token will be generated automatically

To view the token information, copy the token and paste it on the utility https://jwt.ms/

If your token has a scp (Scope) claim, then it’s a user based token (Delegated permissions). It is a JSON string containing a space separated list of scope the use has access to call different graph endpoints. You can also find other information related to the issued token, token issued at (iat), expirty not before (nbf), expiry time (exp). The data is in UNIX time stamp but you can convert this information to standard time using the online URL

https://www.epochconverter.com/

More information about JWT can be found at

https://auth0.com/docs/tokens/json-web-tokens

Postman Client:

Postman is a tool that can be used to build and test requests using the Microsoft graph API’s. To use this tool for testing the Graph API endpoint’s, register an app in Azure Active directory as per the instructions from this blog post. Provide the permission (Delegated & Application) as per your need to test it using Postman.

Copy the client id, client secret & tenant ID of the registered app. To access the various endpoints like authorization and token, click on the Endpoints from the Overview section of the Active directory app.

Setting up the environment using Postman collections:

There are Postman collections with many MS graph API requests created by Microsoft for us to explore. Import the collections and setup the environment (Client ID, Client secret, tenant id) for Application API calls and on-behalf-of API calls as per the instruction from the following article

https://docs.microsoft.com/en-us/graph/use-postman

Application API Token:

To generate an application token, make a POST request to Get App-Only Access Token from the collection Microsoft Graph. The grant_type is client_credentials since it is Application permissions.

Token Validity:

The token is valid for 3599 seconds which is 1 hour. Post that the token will expire, you will have to regenerate the token by making another call.

The AccessToken (Application API call) will be generated and automatically stored on the Environment (Microsoft Graph environment) AppAccessToken with the help of a script on the Tests tab in Postman. Copy the access token value & paste it on the utility https://jwt.ms/. Find the decoded token below which has information like the Application ID/client id of the AD app, display name and roles to which the app has access to poll the graph endpoint.

Graph API call:

The call to the Graph should have the bearer token

Signed-in user/on-behalf-of API Token:

To generate a Signed-in user token, make a POST request to Get user Access Token from the collection Microsoft Graph. The grant_type is password since it is delegated permissions.

The AccessToken (Signed-in user API call) will be generated and automatically stored on the Environment (Microsoft Graph environment) UserAccessToken with the help of a script on the Tests tab in Postman.

Copy the access token value & paste it on the utility https://jwt.ms/. Find the decoded token below which has information like the Application ID/client id of the AD app, display name and scopes (scp) to which the app has access to poll the graph endpoint. If you remember the Application API token had roles & not scopes, so this is how you can identify the token type.

Storing the production User ID and password is not recommended on the Environmental variables since the information is stored in Postman but this can be handled by generating an access token from the request Authorization tab, set the type as OAuth 2.0 and click Get New Access Token button

Fill in all the information gathered from the App in Azure AD like Appid, Secret, Endpoints (Authorization and Token), state can be any random value

Click Request token, this will prompt the user to enter the Username and password. After authentication, it will generate the token which could be used further to make API calls.

Graph API call:

The call to the Graph should have the bearer token on the Authorization tab or on the Headers tab

Summary: On this post we have seen how to use tools like Graph explorer & Postman to test different MS graph API endpoints. You can make requests like GET, POST, PUT, PATCH, DELETE based on its availability. Refer to the Microsoft documentation for v1.0 and beta endpoints. Once you have explored & tested the API, you are ready to use on applications using the available SDK’s for different programming languages. Let me know any feedback or comments on the comment section below