How to get log analytics workspace usage details via api

Try using log analytics query rest api to query Usage table, it works well at my side.

[CmdletBinding()]
param (
    [Parameter(Mandatory)]
    [string]$WorkspaceId,
    [Parameter(Mandatory)]
    [string]$TenantId,
    [Parameter(Mandatory)]
    [string]$ClientId,
    [Parameter(Mandatory)]
    [string]$ClientSecret
)

$headers = @{
    "Content-Type" = "application/x-www-form-urlencoded"
}

$uri = "https://login.microsoftonline.com/$TenantId/oauth2/token"

$body = @{
    grant_type    = "client_credentials"
    resource      = 'https://api.loganalytics.io'
    client_id     = $ClientId
    client_secret = $ClientSecret
}

$token = Invoke-RestMethod -Method Post -Uri $uri -Body $body -Headers $headers


$headers1 = @{
    "Content-Type" = "application/json"
    "Authorization" = "Bearer " + $token.access_token
}

$uri1 = "https://api.loganalytics.io/v1/workspaces/$WorkspaceId/query"

$queryString = "Usage | where TimeGenerated  > startofday(ago(31d)) | where IsBillable == true | extend isSecurity = DataType in ('WindowsEvent','SecurityAlert','SecurityBaseline','SecurityBaselineSummary','SecurityDetection','SecurityEvent','WindowsFirewall','MaliciousIPCommunication','LinuxAuditLog','SysmonEvent','ProtectionStatus') | summarize TotalVolumeGB = sum(Quantity) / 1000 by bin(TimeGenerated, 1d), isSecurity, DataType| sort by TimeGenerated asc"

$body1 = @{
    query = $QueryString
}

$bodyString = $body1 | ConvertTo-Json -Depth 10

$response = Invoke-RestMethod -Method Post -Uri $uri1 -Body $bodyString -Headers $headers1

$response