PowerShell and REST APIs: consume and automate external services

PowerShell is a first-class HTTP client with Invoke-RestMethod and Invoke-WebRequest. Combined with its native ability to handle JSON and XML, it is ideal for integrating external APIs into automations without extra code.

OAuth2 authentication (Client Credentials)

# Get an access token (Azure AD / Entra ID)
$body = @{
    grant_type    = "client_credentials"
    client_id     = $env:APP_CLIENT_ID
    client_secret = $env:APP_CLIENT_SECRET
    scope         = "https://graph.microsoft.com/.default"
}

$tokenResponse = Invoke-RestMethod `
    -Method POST `
    -Uri "https://login.microsoftonline.com/$env:TENANT_ID/oauth2/v2.0/token" `
    -ContentType "application/x-www-form-urlencoded" `
    -Body $body

$token = $tokenResponse.access_token

GET with authentication headers

# Reusable headers
$headers = @{
    Authorization  = "Bearer $token"
    "Content-Type" = "application/json"
}

# GET call
$users = Invoke-RestMethod `
    -Method GET `
    -Uri "https://graph.microsoft.com/v1.0/users" `
    -Headers $headers

$users.value | Select-Object displayName, mail | Format-Table

Automatic pagination

# Collect all result pages
$url     = "https://graph.microsoft.com/v1.0/users?$top=100"
$results = @()

do {
    $response = Invoke-RestMethod -Uri $url -Headers $headers -Method GET
    $results += $response.value
    $url = $response."@odata.nextLink"
} while ($url)

Write-Output "Total users: $($results.Count)"

POST — create resources via API

# Create a group via the Graph API
$body = @{
    displayName     = "Analytics Team"
    mailEnabled     = $false
    securityEnabled = $true
    mailNickname    = "analytics-team"
} | ConvertTo-Json

Invoke-RestMethod `
    -Method POST `
    -Uri "https://graph.microsoft.com/v1.0/groups" `
    -Headers $headers `
    -Body $body

Conclusion

PowerShell + Invoke-RestMethod covers 95% of integrations with modern APIs. For enterprise automations that combine M365, Azure and external systems with no dedicated SDK, it is the fastest to implement and easiest to maintain.