[stphnwlsh]

Summary

The Inspector warns on every tool with a nullable field, because the generated schemas write "type": ["string", "null"]. It's valid JSON Schema, but clients that map schemas onto a single-type dialect, such as Gemini's function declarations, can reject it or drop the constraint. PortableSchemaFilter now rewrites those fields to an anyOf of single types when tools are listed, in input and output schemas, and the Inspector shows no warnings on any tool.

This is a temporary workaround for Gemini-style clients, and we'll remove it when they handle type arrays.

It's a list-tools filter because WithToolsFromAssembly doesn't expose SchemaCreateOptions, so TransformSchemaNode would mean replacing the SDK's tool scan with our own.

The other templates don't need this. Minimal API, Web API and GraphQL don't publish MCP tool schemas.

Related issues

None.

Type of change

• Bug fix
• New feature
• Breaking change (the generated solution or template parameters change in a way existing users will notice)
• Refactoring or clean-up
• Documentation
• Build, pipeline or dependency update

Shared layers

• This only touches the Presentation layer of this template.
• This touches the Application or Infrastructure layers, tests, pipeline or repository setup, so it needs to be carried across all five templates.

Checklist

• dotnet build and dotnet test pass locally with no warnings.
• I added or updated tests, and line coverage stays at or above 95%.
• I updated the README or docs where behaviour changed.
• If this changes how we do something, I updated the matching skill in .agents/skills.
• I checked the template still installs and creates a working solution (see CONTRIBUTING.md).

[github-actions]

Build Pipeline

✅ Ready to merge. Every stage passed.

Stage	Result	Details
Build	🟢 Passed	Version 2026.11.06.190-pr-50 · Template package 233 KB
Test	🟢 Passed	249 passed · 0 failed · 0 skipped · Template installs, builds and passes its tests
Coverage	🟢 Passed	100% (836 of 836 lines) · Needs 95%
Static Analysis	🟢 Passed	No open CodeQL alerts
Dependency Review	🟢 Passed	0 vulnerable packages · 0 licence problems
Container Scan	🟢 Passed	Image starts and answers · No open Trivy alerts

_{Commit ffc7aff · Full run}