mcp-server copilot-instructions.md

Copilot Instructions

Build

# Build (requires BC DevTools DLLs, see below)
dotnet build --configuration Release

# Run tests
dotnet test --configuration Release

# Pack as .NET global tool
dotnet pack src/ALCops.Mcp/ALCops.Mcp.csproj --configuration Release --output ./artifacts

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BC DevTools dependency

The project references proprietary Microsoft BC Development Tools DLLs (Microsoft.Dynamics.Nav.CodeAnalysis, .Workspaces, .Analyzers.Common). These are not bundled and must exist locally for compilation. The BcDevToolsDir MSBuild property (default: ../../Microsoft.Dynamics.BusinessCentral.Development.Tools) points to the directory containing a net8.0/ subfolder with these DLLs.

At runtime, BcDevToolsBootstrap resolves them automatically through a fallback chain: BCDEVELOPMENTTOOLSPATH env var → AL VS Code extension → NuGet cache → auto-download from NuGet.

Architecture

This is an MCP (Model Context Protocol) server packaged as a .NET 8 global tool (alcops-mcp). It exposes AL code analysis capabilities over stdio JSON-RPC.

Startup sequence (order matters)

1. Program.cs calls BcDevToolsBootstrap.ResolveAndRegister() to find BC DevTools and register an AssemblyLoadContext resolver. This must happen before any BC types are JIT-compiled.
2. McpHost.RunAsync() is marked [NoInlining] to enforce this ordering, then builds the host, registers DI services, and starts the MCP stdio transport.

Key layers

• Tools/ — MCP tool endpoints. Each class is annotated with [McpServerToolType] and methods with [McpServerTool]. Tools are auto-discovered via WithToolsFromAssembly(). The five tools: analyze, list_rules, get_fixes, apply_fix, apply_fix_all.
• Services/ — Core logic. Services are registered as singletons in McpHost.
  • ProjectSessionManager — Caches loaded AL project workspaces keyed by path. GetOrLoadProjectAsync is the main entry point tools use.
  • AnalyzerRegistry — Loads ALCops' 6 built-in cops at startup via reflection. Indexes analyzers, code fix providers, and diagnostic descriptors.
  • ProjectAnalyzerResolver — Merges built-in analyzers with external ones (BC standard cops like ${CodeCop}, third-party DLLs). Reads analyzer config from .vscode/settings.json (al.codeAnalyzers). Also loads rulesets from multiple sources (.vscode/settings.json, .AL-Go/settings.json, convention-named files).
  • ExternalAnalyzerLoader — Loads third-party analyzer DLLs into isolated AssemblyLoadContext instances.
  • ProjectLoader — Creates an AlProjectWorkspace from disk (reads app.json, enumerates .al files, resolves .alpackages).
• Models/ — Simple record types for tool return values. Serialized with JsonDefaults.Options (camelCase, not indented).