Uses docdb rest api from powershell to list the collections

listDocDbCollections.ps1

$InstanceUrl = "https://something.documents.azure.com:443"
$DatabaseName = "dbname"
$AccessKey = "accesskey"

#Create a signiture for docdb in powershell
function Get-Signature {
    param(
        [parameter(Mandatory=$true)]
        [string]$verb,
        [parameter(Mandatory=$true)]
        [string]$resourceType,
        [parameter(Mandatory=$true)]
        [string]$resourceLink,
        [parameter(Mandatory=$true)]
        [string]$dateString
    )

    $authHeader = "$verb`n$resourceType`n$resourceLink`n$dateString`n`n"

    write-host $authHeader

    $hmacsha = New-Object System.Security.Cryptography.HMACSHA256
    $hmacsha.key = [Convert]::FromBase64String($AccessKey)
    $signature = $hmacsha.ComputeHash([Text.Encoding]::UTF8.GetBytes($authHeader))
    $signature = [Convert]::ToBase64String($signature)

    $headerRaw = "type=master&ver=1.0&sig=$signature"

    return [System.Web.HttpUtility]::UrlEncode($headerRaw) 
}




$dateString = (Get-Date -Format R).ToLowerInvariant()

$header = Get-Signature "get" "colls" "dbs/$DatabaseName" $dateString

$collections = Invoke-WebRequest -Uri "$InstanceUrl/dbs/$DatabaseName/colls" -Headers @{ 
    "Authorization" = $header
    "x-ms-version" = "2015-12-16" 
    "x-ms-date" = $dateString
} | ConvertFrom-Json

$collections