Add MCP gateway auto-discovery integrations for chat clients and agents

[KSemenenko]

Summary

• add a reusable McpGatewayAutoDiscoveryChatClient and UseManagedCodeMcpGatewayAutoDiscovery(...) wrapper for staged tool exposure in chat loops
• extend McpGatewayToolSet with discovered proxy-tool creation and add the shorter AddMcpGatewayTools(...) chat-options API
• add scenario-driven integration coverage for direct IChatClient and Microsoft Agent Framework flows against a 50-tool catalog in both lexical fallback mode and vector mode
• rewrite the README as consumer-facing onboarding and update architecture/ADR docs for the shipped auto-discovery flow

Testing

• dotnet restore ManagedCode.MCPGateway.slnx
• dotnet build ManagedCode.MCPGateway.slnx -c Release --no-restore
• dotnet build ManagedCode.MCPGateway.slnx -c Release --no-restore -p:RunAnalyzers=true
• dotnet test --solution ManagedCode.MCPGateway.slnx -c Release --no-build
• cloc src tests
• roslynator analyze src/ManagedCode.MCPGateway/ManagedCode.MCPGateway.csproj tests/ManagedCode.MCPGateway.Tests/ManagedCode.MCPGateway.Tests.csproj --severity-level warning

[chatgpt-codex-connector]

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[Copilot]

Pull request overview

This PR adds staged MCP gateway auto-discovery for chat clients and agents. It introduces McpGatewayAutoDiscoveryChatClient (and its UseManagedCodeMcpGatewayAutoDiscovery extension), the CreateDiscoveredTools/AddTools additions to McpGatewayToolSet, and integration tests covering both direct IChatClient and Microsoft Agent Framework scenarios against a 50-tool catalog in lexical and vector modes. It also rewrites the README as consumer-facing onboarding and adds a new ADR.

Changes:

• New McpGatewayAutoDiscoveryChatClient and UseManagedCodeMcpGatewayAutoDiscovery wrapper for staged per-turn tool exposure in chat loops
• Extended McpGatewayToolSet with CreateDiscoveredTools/AddTools and new ChatOptions.AddMcpGatewayTools extension; AddManagedCodeMcpGatewayTools marked obsolete
• Integration tests (McpGatewayChatClientIntegrationTests, McpGatewayAgentFrameworkIntegrationTests) and enriched test helpers (TestChatClient with scenario support, GatewayIntegrationTestSupport); README/ADR/docs updated

Reviewed changes

Copilot reviewed 18 out of 18 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/ManagedCode.MCPGateway/McpGatewayAutoDiscoveryChatClient.cs	New: per-request staged tool-discovery chat client wrapper
src/ManagedCode.MCPGateway/McpGatewayToolSet.cs	Extended: AddTools, CreateDiscoveredTools, proxy-tool creation
src/ManagedCode.MCPGateway/Registration/McpGatewayChatOptionsExtensions.cs	New: AddMcpGatewayTools + obsolete shims
src/ManagedCode.MCPGateway/Registration/McpGatewayChatClientExtensions.cs	New: UseManagedCodeMcpGatewayAutoDiscovery extension
src/ManagedCode.MCPGateway/Configuration/McpGatewayAutoDiscoveryOptions.cs	New: options for max tools, tool names
src/ManagedCode.MCPGateway/Internal/Serialization/McpGatewayJsonSerializer.cs	Added JsonStringEnumConverter to serializer options
tests/ManagedCode.MCPGateway.Tests/ChatClient/McpGatewayChatClientIntegrationTests.cs	New: integration tests for direct IChatClient auto-discovery
tests/ManagedCode.MCPGateway.Tests/Agents/McpGatewayAgentFrameworkIntegrationTests.cs	New: integration tests for Agent Framework auto-discovery
tests/ManagedCode.MCPGateway.Tests/TestSupport/TestChatClient.cs	Extended: scenario-driven invocation capture
tests/ManagedCode.MCPGateway.Tests/TestSupport/GatewayIntegrationTestSupport.cs	New: 50-tool catalog + scenario builders + flow assertions
tests/ManagedCode.MCPGateway.Tests/TestSupport/TestEmbeddingGenerator.cs	New CreateVector hook for semantic vector tests
tests/ManagedCode.MCPGateway.Tests/ManagedCode.MCPGateway.Tests.csproj	Added Microsoft.Agents.AI package reference
Directory.Packages.props	Added Microsoft.Agents.AI 1.0.0-rc3; bumped ModelContextProtocol to 1.1.0 and TUnit to 1.19.0
docs/ADR/ADR-0003-reusable-chat-client-and-agent-tool-modules.md	New ADR documenting the AITool-module approach
docs/Architecture/Overview.md	Updated architecture diagrams and module map
README.md	Rewritten as consumer-facing onboarding
AGENTS.md	New coding rules added

---

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[KSemenenko]

Addressed all open review comments in 3dd9938.

Covered fixes:

• ignore primitive/malformed gateway_tools_search payloads during auto-discovery replay
• make McpGatewayToolSet.AddTools(...) return a composed copy instead of mutating the input list
• normalize discovered tool names so they never start with a digit
• rename the public chat-client extension to UseMcpGatewayAutoDiscovery(...)
• remove obsolete chat-options legacy aliases and redundant test assertions

Verification:

• dotnet restore ManagedCode.MCPGateway.slnx
• dotnet build ManagedCode.MCPGateway.slnx -c Release --no-restore
• dotnet build ManagedCode.MCPGateway.slnx -c Release --no-restore -p:RunAnalyzers=true
• dotnet test --solution ManagedCode.MCPGateway.slnx -c Release --no-build
• roslynator analyze src/ManagedCode.MCPGateway/ManagedCode.MCPGateway.csproj -p Configuration=Release --severity-level warning
• roslynator analyze tests/ManagedCode.MCPGateway.Tests/ManagedCode.MCPGateway.Tests.csproj -p Configuration=Release --severity-level warning
• cloc --include-lang=C# src tests

[KSemenenko]

#3 contains all implemention