debuggervisualizer – Can’t create a MS Visual Studio visualizer

I have a simple decimal class with the following visualizer:

<?xml version="1.0" encoding="utf-8"?>
<AutoVisualizer xmlns="http://schemas.microsoft.com/vstudio/debugger/natvis/2010">
  <Type Name="awl::decimal&lt;*,*,*&gt;">
    <DisplayString>{to_astring()}</DisplayString>
    <Expand>
      <Item Name="Value">{to_astring()}</Item>
      <Item Name="Mantissa">{m_data.man()}</Item>
      <Item Name="Exponent">{m_data.exp()}</Item>
      <Item Name="Positive">{m_data.positive()}</Item>
      <Item Name="Denominator">{m_denoms[m_data.exp()]}</Item>
      <Item Name="RawBits">{to_bits()}</Item>
    </Expand>
  </Type>
</AutoVisualizer>

I added the visualizer to .vsproj:

<?xml version="1.0" encoding="utf-8"?>
<Project DefaultTargets="Build" ToolsVersion="17.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <ItemGroup>
    <Natvis Include="Ide\VisualStudio\Awl.natvis" />
  </ItemGroup>
  ...
</Project>

but it does not work.

What is wrong?

Should I add the file to some “Visualizers” group?