Azure DevOps agent pool: How do I demand a specific net framework SDK capability?

We run self-hosted agents for our dev.azure.com pipelines. Some projects require specific NetFramework or NetCore versions but we don't want to install 20 years of old versions on all agent machines. (There are lots of SDK versions).

I can see that agent capabilities and demands provide the functionality to make sure a build is only run on a capable agent.

But how do I specify a demand for a specific NetFramework SDK version e.g. 4.8.1? I can't find a list of well known capability names that an agent might report.

No sure whether some of your agents have such capabilities as those of one of my agent's in the Default self-hosted pool below. If not, you may add a user-defined capablity to demand the agent job to run on the expected agents.

Taking my YAML pipeline for example, either agent job managed to pick up the expected agents.

jobs:
- job: ReferenceSystemCapabilities
  pool: 
    name: Default
    demands:
    - Agent.OS -equals Windows_NT
    - DotNetFramework_4.8.0
    - DotNetFramework_4.8.0_x64
  steps:
  - pwsh: |
      Get-ChildItem -Path 'HKLM:\SOFTWARE\Microsoft\NET Framework Setup\NDP' -Recurse |
      Get-ItemProperty -Name Version,Release -ErrorAction SilentlyContinue |
      Where-Object { $_.PSChildName -match '^(?!S)\p{L}'} |
      Select-Object PSChildName, Version, Release

- job: ReferenceUserDefinedCapabilities
  pool: 
    name: Default
    demands:
    - DotNetFrameworkVersion -equals 4.8.0
  steps:
  - pwsh: |
      Get-ChildItem -Path 'HKLM:\SOFTWARE\Microsoft\NET Framework Setup\NDP' -Recurse |
      Get-ItemProperty -Name Version,Release -ErrorAction SilentlyContinue |
      Where-Object { $_.PSChildName -match '^(?!S)\p{L}'} |
      Select-Object PSChildName, Version, Release