Azure Cost Management API

Azure Cost Management API

The Problem

In PowerShell, inline JSON for Cost Management API causes "Unsupported Media Type" errors:

# This fails silently or with 415 error
az rest --method POST --uri $uri --body '{"type":"Usage","timeframe":"MonthToDate"}'

The shell mangles the JSON.

The Solution

Write JSON to a file, then reference with @:

# 1. Create body file
$body = @{
    type = "Usage"
    timeframe = "MonthToDate"
    dataset = @{
        granularity = "Daily"
        aggregation = @{
            totalCost = @{
                name = "Cost"
                function = "Sum"
            }
        }
    }
} | ConvertTo-Json -Depth 10

$bodyFile = "$env:TEMP\cost-query-body.json"
$body | Out-File -FilePath $bodyFile -Encoding utf8

# 2. Call with file reference
$uri = "/subscriptions/$subscriptionId/providers/Microsoft.CostManagement/query?api-version=2023-03-01"
az rest --method POST --uri $uri --body "@$bodyFile"

Common Queries

Monthly Cost by Resource Group

{
  "type": "Usage",
  "timeframe": "MonthToDate",
  "dataset": {
    "granularity": "None",
    "aggregation": {
      "totalCost": { "name": "Cost", "function": "Sum" }
    },
    "grouping": [
      { "type": "Dimension", "name": "ResourceGroup" }
    ]
  }
}

Daily Cost Trend

{
  "type": "Usage",
  "timeframe": "MonthToDate",
  "dataset": {
    "granularity": "Daily",
    "aggregation": {
      "totalCost": { "name": "Cost", "function": "Sum" }
    }
  }
}

Verification

# Should return JSON with "rows" array
$result = az rest --method POST --uri $uri --body "@$bodyFile" | ConvertFrom-Json
$result.properties.rows | Format-Table

When to Apply

• Any Azure Cost Management API call from PowerShell
• Complex JSON bodies in az rest commands
• Budget alerts and cost analysis scripts

Tags

azure cost-management api powershell