A bit of PowerShell to add capabilities to a Azure DevOps Pipeline Agent programmatically

Add-CapabilityToAgent.ps1

##-----------------------------------------------------------------------
## <copyright file="Add-CapabilityToAgent.ps1">(c) Tichard Fennell </copyright>
##-----------------------------------------------------------------------
# Adds capacility tags a Azure DevOps Pipeline agent
# Run in the agent folder
Param
(
    [parameter(Mandatory=$true,HelpMessage="Personal Access Token with rights to manage agents")]
    $patToken,

    [parameter(Mandatory=$false,HelpMessage="The tags to added as a block of JSON ")]
    $tags = "{SONAR_SCANNER:'true',UxTest:'true'}",
    
    [parameter(Mandatory=$true,HelpMessage="The Azure DevOps instance target name")]
    $organisation
)

function Get-WebClient
{
 param
    (
        [string]$username, 
        [string]$password,
        [string]$contentType = "application/json"
    )

    $wc = New-Object System.Net.WebClient
    $wc.Headers["Content-Type"] = $contentType
    
    if ([System.String]::IsNullOrEmpty($password))
    {
        $wc.UseDefaultCredentials = $true
    } else 
    {
       # This is the form for basic creds so either basic cred (in TFS/IIS) or alternate creds (in VSTS) are required"
       $pair = "${username}:${password}"
       $bytes = [System.Text.Encoding]::ASCII.GetBytes($pair)
       $base64 = [System.Convert]::ToBase64String($bytes)
       $wc.Headers.Add("Authorization","Basic $base64");
    }
 
    $wc
}

Write-Host "Getting the agent details"
$agent = (Get-Content '.agent' | Out-String | ConvertFrom-Json)

Write-host "Adding tags"
$wc = Get-WebClient -password $patToken
$uri = "https://$organisation.visualstudio.com/_apis/distributedtask/pools/$($agent.poolId)/agents/$($agent.agentId)/usercapabilities?api-version=5.0-preview.1"
$response = $wc.UploadString($uri,"PUT", $tags )| ConvertFrom-Json