RoselineMCP

Roslyn code intelligence for AI coding agents, over MCP. Give Claude, Cursor, and Copilot a semantic view of your C# solution — symbols, references, call graphs, surgical edits — so they navigate by structure instead of re-reading source. Measured 89% fewer tokens (median) →

📖 Documentation, tool reference & the honest benchmark →

Why RoselineMCP
Quick Start
Features
Tech Stack
Getting Started
MCP Client Compatibility
Available Tools
Tool Annotations
Tool Compatibility Policy
Architecture
Project Structure
Security
Documentation
Roadmap
Contributing
License
Acknowledgments

Why RoselineMCP

Your coding agent shouldn't read a 700-line file to change one method. Source code dominates an agent's token budget, so the cheapest win is to stop feeding it whole files.

RoselineMCP wraps the Roslyn compiler platform as an MCP server. Instead of dumping source into the model, it answers structural questions precisely — where is this symbol used, what implements this interface, who calls this method, what's the shape of this file — and it edits surgically: a member-level diff, not a whole-file rewrite.

On RoselineMCP's own source, the read-only navigation tools returned a median 89% fewer tokens per task (pooled, size-weighted: 93%) than reading the corresponding files — measured honestly, weak cases included.

search_symbols on Program.cs: 1,638 tokens → 71 (−96%). The agent gets the shape of the file; you skip the wall.

Quick Start

Any MCP client that speaks dnx (the .NET equivalent of npx) runs it on demand — no install step. Requires the .NET 10 SDK.

// claude_desktop_config.json  ·  .vscode/mcp.json  ·  ~/.cursor/mcp.json
{
  "mcpServers": {
    "roseline": { "command": "dnx", "args": ["RoselineMCP", "--yes"] }
  }
}

Then ask your agent to "find every caller of OrderService.Checkout" or "rename Foo to Bar across the solution." Prefer a pinned NuGet install or Docker? See Getting Started.

Features

Token-efficient code navigation -- symbols, references, call graphs, type hierarchies, and file outlines via Roslyn instead of whole files. A measured 89% median token reduction per task (93% pooled, size-weighted) -- see the benchmark.
Surgical code edits -- replace/add/delete a member or rename a symbol solution-wide, emitting a unified diff instead of a whole-file rewrite. Preview by default.
Comprehensive analysis & auto-fix -- diagnostics across a solution (Roslyn + Roslynator) with automated fixes and reviewable patches.
Read-only by default -- the seven navigation tools and the diagnostics/patch tools never touch disk; the three write tools require an explicit previewOnly: false.
Works with your client -- Claude Desktop, VS Code (Copilot / MCP), Cursor. Install via dnx, NuGet global tool, or Docker.
Honest, reproducible benchmark -- run it against your own solution: dotnet run --project RoselineMCP.TokenBenchmark -c Release.

Tech Stack

Layer	Technology
Runtime	.NET 10.0
Compiler Platform	Roslyn (Microsoft.CodeAnalysis) 5.6.0
Analyzers	Roslynator 4.15.0
MCP SDK	ModelContextProtocol 1.4.0
Diff Engine	DiffPlex 1.9.0
Build System	MSBuild 18.7.1
Hosting	Microsoft.Extensions.Hosting 10.0.9

Versions above are kept in sync with RoselineMCP/RoselineMCP.csproj — that file is the source of truth if this table ever drifts.

Getting Started

Prerequisites

NuGet global tool: .NET 10.0 SDK or later
Docker: Docker Desktop or Docker Engine
Build from source: .NET 10.0 SDK + MSBuild (included with Visual Studio or .NET SDK)
MCP client: Claude Desktop or any MCP-compatible client

Installation

Claude Desktop, one click: download RoselineMCP.mcpb from the latest release and open it — Claude Desktop shows an install dialog, no config editing. (It launches via dnx under the hood, so the .NET 10 SDK is still required.) Prefer to edit config yourself, or using another client? Use one of the options below.

Option 1 -- dnx (no install step) (recommended)

RoselineMCP ships an MCP server registry manifest, so any MCP client that understands the dnx launcher (the .NET equivalent of npx — resolves and runs a NuGet-packaged tool on demand, without a separate dotnet tool install step) can start it directly. Requires the .NET 10.0 SDK.

{
  "mcpServers": {
    "roseline": {
      "command": "dnx",
      "args": ["RoselineMCP", "--yes"]
    }
  }
}

Add this to your Claude Desktop or VS Code MCP configuration (see MCP Client Compatibility below for exact file locations per client). dnx downloads and caches the tool on first use, so there's nothing to pre-install globally.

Option 2 -- NuGet Global Tool (offline / pinned-version installs)

Requires .NET 10.0 SDK or later.

dotnet tool install -g RoselineMCP

After installation, the roseline-mcp command is available globally.

Claude Desktop configuration (NuGet global tool)

Add to your Claude Desktop configuration file (claude_desktop_config.json):

{
  "mcpServers": {
    "roseline": {
      "command": "roseline-mcp"
    }
  }
}

Config file location:

macOS: ~/Library/Application Support/Claude/claude_desktop_config.json

Windows: %APPDATA%\Claude\claude_desktop_config.json

Option 3 -- Docker

No SDK required. Works on any platform with Docker installed.

docker run -i --rm phmatray/roseline-mcp:latest

Claude Desktop configuration (Docker)

{
  "mcpServers": {
    "roseline": {
      "command": "docker",
      "args": [
        "run",
        "-i",
        "--rm",
        "phmatray/roseline-mcp:latest"
      ]
    }
  }
}

Note: The -i flag is required for stdio transport. The --rm flag removes the container after the session ends.

Option 4 -- Build from Source

git clone https://github.com/Atypical-Consulting/RoselineMCP.git
cd RoselineMCP
dotnet build
dotnet test

Claude Desktop configuration (build from source)

{
  "mcpServers": {
    "roseline": {
      "command": "dotnet",
      "args": ["run", "--project", "/path/to/RoselineMCP/RoselineMCP.csproj"]
    }
  }
}

MCP Client Compatibility

RoselineMCP speaks plain stdio MCP, so it should work with any MCP-compatible client. The snippets below are documented, not independently verified in every case — we've confirmed the protocol-level behavior (stdio transport, tool discovery, JSON responses) works correctly, but we have not personally exercised each client's own configuration UI/file end to end. If one of these doesn't work as written for your client version, please open an issue.

Edit claude_desktop_config.json (see file locations under Installation above) and add a roseline entry under mcpServers, using any of the four install options shown above (dnx, global tool, Docker, or build-from-source).

Add an entry to your workspace or user mcp.json (Command Palette → "MCP: Open User Configuration", or .vscode/mcp.json in the workspace):

{
  "servers": {
    "roseline": {
      "command": "dnx",
      "args": ["RoselineMCP", "--yes"]
    }
  }
}

Substitute "command": "roseline-mcp" (no args) if you installed via the NuGet global tool instead.

Add a roseline entry to ~/.cursor/mcp.json (global) or .cursor/mcp.json (project-local), using the same command/args shape as the VS Code snippet above.

Available Tools

1. AnalyzeSolution

Analyzes an entire C# solution for diagnostics. Read-only — never modifies files on disk. pathOrGit also accepts an http(s):// Git URL, which is shallow-cloned to a temp directory, analyzed, and deleted afterward.

analyzeSolution({
  pathOrGit: "/path/to/solution.sln",
  include: "Core",              // Optional: only project names containing this substring
  exclude: "Test",              // Optional: skip project names containing this substring
  severity: "warning",          // Optional: minimum severity (Error|Warning|Info|Hidden)
  maxDiagnostics: 100           // Optional: Maximum diagnostics to return (default: 100)
})

Returns: solution file name, project count, a diagnosticSummary (counts by severity), and a topDiagnostics array with project/file/line/column/id/severity/message per diagnostic.

2. ListDiagnostics

Gets detailed diagnostics for a specific project. Read-only — never modifies files on disk. project is optional and accepts the same references as the navigation tools (name, directory, .csproj, or .sln path); when omitted, the solution/project is auto-discovered from the working directory.

listDiagnostics({
  project: "MyProject.csproj",     // Optional: name, directory, .csproj, or .sln; auto-discovered if omitted
  ids: ["CS0168", "CS0219"],       // Optional: Filter by diagnostic IDs
  files: ["Controller.cs"],        // Optional: substring match against each diagnostic's file path (case-insensitive; NOT a glob pattern)
  max: 50                          // Optional: Maximum results
})

Returns: project name, totalDiagnostics count, the filtered diagnostics list, stats (counts grouped by ID and by severity), and suggestedFixableIds — diagnostic IDs a code fix provider is actually registered for.

3. ApplyFixes

Applies automated code fixes for specified diagnostics. Defaults to preview mode: previewOnly defaults to true, so calling this tool without setting it never writes to disk — you must pass previewOnly: false explicitly to apply changes. project is optional and accepts the same references as the navigation tools (name, directory, .csproj, or .sln path); when omitted, the solution/project is auto-discovered from the working directory.

applyFixes({
  ids: ["CS0168", "RCS1001"],   // Diagnostic IDs to fix
  project: "MyProject.csproj",  // Optional: name, directory, .csproj, or .sln; auto-discovered if omitted
  previewOnly: false             // Optional (default: true). Set false to write changes to disk.
})

Returns: project name, fixedCount, fixersApplied (diagnostic IDs actually fixed), changedFiles (solution-root-relative, forward slashes — the same path base as the navigation tools), a unified diff patch, notes (skipped/failed IDs and status messages), and previewOnly echoing back whether anything was written.

4. CreatePatch

Generates a unified diff between two text versions. Read-only — operates purely on the provided strings, never touches the filesystem.

createPatch({
  before: "original code",
  after: "modified code",
  fileName: "Example.cs",        // Optional: For display in diff
  ignoreWhitespace: false,       // Optional: ignore whitespace-only differences
  ignoreCase: false              // Optional: ignore case differences
})

Returns: the unified diff patch, hasChanges, linesAdded, linesRemoved, and the fileName/summary used in the diff header.

Code Navigation Tools (read-only)

These tools return precise structure instead of whole files, so an AI agent can orient itself in a codebase while spending far fewer tokens than reading source directly. All are read-only and take an optional project (name, directory, .csproj path, or .sln path) — when omitted, RoselineMCP auto-discovers the solution/project from its working directory. When the project belongs to a solution, the whole solution is loaded and symbol search/resolution spans every project in it (including sibling projects the requested project doesn't reference), so references/renames span projects. Full request/response shapes are in docs/API.md.

Tool names on the wire are snake_case. The section headings below use friendly PascalCase/camelCase for readability, but the actual MCP tool names returned by tools/list (and expected by tools/call) are: search_symbols, get_symbol_info, find_references, find_implementations, get_call_graph, get_type_hierarchy, get_symbol_at_position, edit_member, rename_symbol (matching the existing analyze_solution / list_diagnostics / apply_fixes / create_patch).

5. SearchSymbols

Find symbols by wildcard/substring name pattern, or outline a single file.

searchSymbols({
  project: "MyApp.Core",
  query: "*Service",             // Substring, or wildcard with * and ? — omit to outline a file
  file: "UserService.cs",        // Optional: restrict to one file, or outline it when query omitted
  kinds: ["class", "method"],    // Optional: filter by kind (also accepts "type" / "member")
  max: 50                        // Optional (default: 50)
})

Returns: symbols (name, fullName, kind, signature, file, line — file paths are solution-root-relative; the single-file outline instead returns name, kind, signature, line, containingType), totalFound, truncated (omitted when not capped).

6. GetSymbolInfo

The compact "go to definition": a symbol's declaration metadata and (optionally) its source.

getSymbolInfo({
  project: "MyApp.Core",
  symbol: "Acme.Users.UserService.GetUser",  // Simple or fully-qualified name
  includeSource: true                          // Optional (default: true)
})

Returns: name, fullName, kind, signature, and (each omitted when empty/absent) modifiers, baseTypes, interfaces, documentation, definitionFile/Line, and source. Accessibility is already part of signature; definitionFile is solution-root-relative.

7. FindReferences

Every use site of a symbol across the solution, as location + one-line snippet.

findReferences({ project: "MyApp.Core", symbol: "GetUser", includeDefinition: false, max: 100 })

Returns: references (file — solution-root-relative, line, snippet), totalReferences, truncated (omitted when not capped).

8. FindImplementations

Implementations of an interface/member, overrides of a virtual/abstract member, or derived types of a class.

findImplementations({ project: "MyApp.Core", symbol: "IRepository", max: 100 })

Returns: implementations (symbol summaries), totalFound, truncated.

9. GetCallGraph

A depth-bounded caller and/or callee graph for a method, with cycle detection.

getCallGraph({
  project: "MyApp.Core",
  method: "Handle",
  direction: "callers",   // "callers" (default) | "callees" | "both"
  depth: 1,               // 1-3 (default: 1)
  max: 50                 // Optional: nodes expanded per direction
})

Returns: callers/callees trees of nodes (fullName with simple parameter-type names, file — solution-root-relative, line, truncated, children). Call GetSymbolInfo for a node's full signature.

10. GetTypeHierarchy

A type's base-class chain, implemented interfaces, and/or derived types.

getTypeHierarchy({
  project: "MyApp.Core",
  type: "SqlRepository",
  direction: "both",   // "base" | "derived" | "both" (default)
  max: 100             // Optional: maximum derived types returned (default: 100)
})

Returns: baseTypes, interfaces, derivedTypes (as symbol summaries).

13. GetSymbolAtPosition

The symbol living at a file:line(:column) position — turn a diagnostic, stack trace, or grep hit into a symbol name without reading the file.

getSymbolAtPosition({
  project: "MyApp.Core",
  file: "UserService.cs",  // File name or path suffix (same matching as SearchSymbols)
  line: 42,                // 1-based
  column: 17               // Optional (1-based) — omit to resolve the most relevant symbol on the line
})

Returns: name, fullName, kind, signature, isDeclaration (whether the position sits on the symbol's own declaration), and (each omitted when empty/absent) containingType, documentation, definitionFile/Line (solution-root-relative). Line-only queries prefer declarations on the line over referenced symbols.

Code Editing Tools (preview by default)

Surgical edits that emit a member-level change rather than a whole-file rewrite. Like ApplyFixes, both default to preview mode (previewOnly: true) — nothing is written to disk unless you pass previewOnly: false explicitly.

11. EditMember

Replace, add, or delete a single type member; returns a unified diff.

editMember({
  project: "MyApp.Core",
  symbol: "Acme.UserService.GetUser",  // The member (replace/delete), or the container type (add)
  operation: "replace",                 // "replace" | "add" | "delete"
  newSource: "public User GetUser(int id) => _repo.Find(id);",  // Required for replace/add
  previewOnly: false                    // Optional (default: true). Set false to write to disk.
})

Returns: operation, target, changedFiles, patch, previewOnly, applied, notes.

12. RenameSymbol

Rename a symbol and update every reference across the solution (Roslyn rename); returns a unified diff.

renameSymbol({ project: "MyApp.Core", symbol: "GetUser", newName: "GetUserById", previewOnly: false })

Returns: symbol, newName, changedFiles, patch, previewOnly, applied, notes.

Tool Annotations

RoselineMCP's SDK (ModelContextProtocol 1.4.0) supports the standard MCP tool annotation hints (readOnlyHint, destructiveHint, idempotentHint), and every tool declares them via [McpServerTool(ReadOnly = ..., Destructive = ..., Idempotent = ...)]:

Tool	readOnlyHint	destructiveHint	idempotentHint	Notes
`AnalyzeSolution`	✅ true	❌ false	✅ true	Never writes to disk.
`ListDiagnostics`	✅ true	❌ false	✅ true	Never writes to disk.
`ApplyFixes`	❌ false	⚠️ true	❌ false	`destructiveHint` is a static, worst-case annotation: it's `true` because the tool can write files when `previewOnly: false` is passed, even though the default call (`previewOnly` unset, i.e. `true`) writes nothing. The SDK's annotation model has no way to express "destructive only for a specific parameter value" — see the doc comment on `ApplyFixesTool.ApplyFixes` in source.
`CreatePatch`	✅ true	❌ false	✅ true	Operates purely on the two provided strings; never touches the filesystem.
`SearchSymbols`	✅ true	❌ false	✅ true	Never writes to disk.
`GetSymbolInfo`	✅ true	❌ false	✅ true	Never writes to disk.
`FindReferences`	✅ true	❌ false	✅ true	Never writes to disk.
`FindImplementations`	✅ true	❌ false	✅ true	Never writes to disk.
`GetCallGraph`	✅ true	❌ false	✅ true	Never writes to disk.
`GetTypeHierarchy`	✅ true	❌ false	✅ true	Never writes to disk.
`GetSymbolAtPosition`	✅ true	❌ false	✅ true	Never writes to disk.
`EditMember`	❌ false	⚠️ true	❌ false	Same worst-case `destructiveHint` rationale as `ApplyFixes`: writes a file only when `previewOnly: false` is passed; the default call writes nothing.
`RenameSymbol`	❌ false	⚠️ true	❌ false	Same worst-case `destructiveHint` rationale as `ApplyFixes`: writes files only when `previewOnly: false` is passed; the default call writes nothing.

These hints are static per-tool metadata for MCP clients that surface them (e.g. to warn a user before an agent invokes a destructive tool) — they describe the tool's worst-case behavior, not the outcome of any specific call. See Tool Compatibility Policy below for the stability guarantees around tool names and parameters that these annotations sit on top of.

Tool Compatibility Policy

Tool names and required parameters are stable within a major version. An MCP client integration written against AnalyzeSolution(pathOrGit, ...) on 1.x will keep working across all 1.x releases.
Optional parameters may be added in minor versions (e.g. CreatePatch gained ignoreWhitespace/ignoreCase as optional, defaulted parameters without breaking existing callers).
Renaming or removing a parameter, changing a parameter's required/optional status, or changing a tool's name is a breaking change. Breaking changes are called out under a dedicated "Breaking Changes" heading in CHANGELOG.md and only ship in a major version bump.
Response shapes (JSON field names/types) are documented in docs/API.md and follow the same policy: additive fields are non-breaking, renamed/removed fields are breaking.

Supported Analyzers

The diagnostics tools (analyze_solution, list_diagnostics, apply_fixes) report compiler diagnostics plus analyzer diagnostics, executed via Roslyn's CompilationWithAnalyzers:

Roslyn Analyzers -- Built-in C# compiler diagnostics
Roslynator -- 500+ analyzers and fixes for C#, bundled with RoselineMCP (shipped as an analyzers/ folder next to RoselineMCP.dll) and executed by default, so RCS* diagnostics surface and are fixable out of the box
Custom Analyzers -- Any Roslyn-based analyzer referenced by your analyzed solution is loaded from the project's analyzer references and run alongside the bundled ones (there is no built-in StyleCop.Analyzers reference — add it to your analyzed solution if you want SA* diagnostics; analyzer-reported rules are auto-fixable only when a matching fixer is loadable)

Set RoselineMCP:RunAnalyzers to false for compiler-only diagnostics (faster on big solutions; see Configuration and the analyzer-execution note in SECURITY.md).

Examples

Analyzing a Solution

# Using with an MCP client
mcp call analyzeSolution '{
  "pathOrGit": "/Users/dev/MyProject/MyProject.sln",
  "severity": "warning",
  "maxDiagnostics": 50
}'

Response:

{
  "solution": "MyProject.sln",
  "projects": 5,
  "diagnosticSummary": {
    "error": 2,
    "warning": 15,
    "info": 28
  },
  "topDiagnostics": [
    {
      "id": "CS0168",
      "severity": "warning",
      "message": "The variable 'ex' is declared but never used",
      "file": "Program.cs",
      "line": 42
    }
  ]
}

Applying Fixes

mcp call applyFixes '{
  "project": "MyProject.Core.csproj",
  "ids": ["CS0168", "RCS1001"],
  "previewOnly": true
}'

Response includes a unified diff patch showing all changes that would be applied.

Configuration

RoselineMCP reads appsettings.json and appsettings.{Environment}.json from the directory the server binary is installed in (AppContext.BaseDirectory) — not from the process working directory. Launching the server from inside a target repository never picks up that repository's own appsettings.json, and the settings packaged with the dotnet tool install are always found. Configuration is read once at startup; there is no reload-on-change file watching.

Environment Variables

Environment variables prefixed with ROSELINE_ override the JSON files, using __ as the section separator. Settings under the RoselineMCP section therefore take a double prefix:

# RoselineMCP:EnableDiagnosticLogging
ROSELINE_RoselineMCP__EnableDiagnosticLogging=true

# RoselineMCP:DefaultTimeout (ms)
ROSELINE_RoselineMCP__DefaultTimeout=300000

# RoselineMCP:RunAnalyzers (compiler-only diagnostics when false)
ROSELINE_RoselineMCP__RunAnalyzers=false

# Logging:LogLevel:RoselineMCP
ROSELINE_Logging__LogLevel__RoselineMCP=Debug

DOTNET_ENVIRONMENT: Set environment (Development, Production)

appsettings.json

Configure logging and other settings:

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "RoselineMCP": "Debug"
    }
  },
  "RoselineMCP": {
    "DefaultTimeout": 120000,
    "EnableDiagnosticLogging": false,
    "WorkspaceCache": true,
    "RunAnalyzers": true
  }
}

RoselineMCP:DefaultTimeout: Wall-clock timeout (ms) applied to each tool call, in addition to the caller's own cancellation. 0 disables it.
RoselineMCP:EnableDiagnosticLogging: Opt-in, local-only tracing of tool invocations — see Debug Logging. Disabled by default; enabled in appsettings.Development.json.
RoselineMCP:WorkspaceCache: Reuse the loaded MSBuild workspace across navigation/edit tool calls (enabled by default) — see Performance. Set to false to load a fresh workspace on every call.
RoselineMCP:RunAnalyzers: Run Roslyn analyzers (bundled Roslynator + the target project's own analyzer references) in the diagnostics tools (enabled by default) — see Supported Analyzers. Set to false for compiler-only diagnostics.

Architecture

RoselineMCP uses stdio transport — this is an intentional design decision. The server runs as a local process launched by the MCP client (Claude Desktop, AI agents), communicates over stdin/stdout, and exits when the client disconnects. This makes it perfectly suited for distribution as a NuGet global tool (dotnet tool install -g RoselineMCP) or Docker image — no port binding, no HTTP server, no infrastructure to manage.

┌─────────────────────┐
│   MCP Client        │
│  (Claude Desktop,   │
│   AI Assistants)    │
└────────┬────────────┘
         │ MCP Protocol (stdio)
         ▼
┌─────────────────────┐
│   RoselineMCP       │
│   MCP Server        │
│                     │
│  ┌───────────────┐  │
│  │  Tool Layer   │  │
│  │  (Analyze,    │  │
│  │   Fix, Patch) │  │
│  └───────┬───────┘  │
│          ▼          │
│  ┌───────────────┐  │
│  │ Service Layer │  │
│  │ (Workspace,   │  │
│  │  Diagnostics) │  │
│  └───────┬───────┘  │
│          ▼          │
│  ┌───────────────┐  │
│  │ Roslyn +      │  │
│  │ Roslynator    │  │
│  │ Analyzers     │  │
│  └───────────────┘  │
└─────────────────────┘
         │
         ▼
┌─────────────────────┐
│  C# Source Code     │
│  (.sln / .csproj)   │
└─────────────────────┘

Project Structure

RoselineMCP/
├── RoselineMCP/
│   ├── Interfaces/       # Service interfaces
│   ├── Services/         # Core business logic
│   ├── Tools/            # MCP tool implementations
│   ├── Models/           # Data transfer objects
│   └── Program.cs        # Application entry point
├── RoselineMCP.Tests/    # Unit tests
├── .github/workflows/    # CI/CD pipelines
├── Dockerfile            # Container build
└── RoselineMCP.sln       # Solution file

Performance

Workspace Cache -- The navigation, edit, and diagnostics/fix tools (ListDiagnostics, ApplyFixes, and everything backed by IProjectLoader) reuse the loaded MSBuildWorkspace across calls, cutting hundreds of milliseconds of reload off every call after the first. Cached entries are fingerprinted (last-write-time + size of the .sln, every .csproj, and every source file, plus their directories) and re-checked on each call, so any change on disk — including RoselineMCP's own edits — triggers a fresh reload. Disable with RoselineMCP:WorkspaceCache = false
Workspace Isolation (AnalyzeSolution) -- AnalyzeSolution still creates a fresh MSBuildWorkspace per operation (see Architecture)
Sequential Project Analysis -- Projects within a solution are analyzed one at a time, not concurrently, to keep MSBuild workspace state consistent
Result Capping -- maxDiagnostics/max bound how many diagnostics are returned per call, independent of how many were found

Security

Read-Only by Default -- AnalyzeSolution, ListDiagnostics, CreatePatch, and all six code navigation tools (SearchSymbols, GetSymbolInfo, FindReferences, FindImplementations, GetCallGraph, GetTypeHierarchy) never write to disk. The three write-capable tools — ApplyFixes, EditMember, and RenameSymbol — each default to previewOnly: true; writing requires the caller to pass previewOnly: false explicitly.
Real, Read-Only Git Cloning -- pathOrGit accepts http(s):// Git URLs, which are shallow-cloned (git clone --depth 1) into a temp directory that's deleted after the operation. No other URL scheme is treated as a Git remote.
MSBuild Is Not a Sandbox -- loading a .sln/.csproj via MSBuildWorkspace is a design-time MSBuild evaluation and can execute build logic embedded in the project (<Exec> tasks, custom UsingTask assemblies, imported .targets/.props). Analyzing a fully untrusted repository or URL carries a real code-execution risk on the host. See SECURITY.md for the full write-up and operator recommendations before pointing RoselineMCP at untrusted input.
Analyzer Execution Is Code Execution -- the diagnostics tools also run the target project's own referenced Roslyn analyzers in-process (see Supported Analyzers); an analyzer from an untrusted repository is arbitrary code. RoselineMCP:RunAnalyzers = false disables all analyzer execution (bundled Roslynator included). See SECURITY.md.
No Dedicated Path-Traversal Sandbox -- paths are resolved with plain existence checks, not canonicalized against an allowed root; treat pathOrGit/project/branch as trusted operator input.

Troubleshooting

Common Issues

MSBuild not found: Ensure .NET SDK is installed and in PATH
Solution won't load: Check for missing NuGet packages, run dotnet restore
No analyzer (RCS/SA) diagnostics found**: Verify RoselineMCP:RunAnalyzers isn't set to false; for non-bundled rule sets (e.g. StyleCop), verify the analyzer is installed in the target project
Permission denied: Ensure read access to solution files

Debug Logging

Enable detailed logging:

ROSELINE_Logging__LogLevel__RoselineMCP=Debug dotnet run --project RoselineMCP/RoselineMCP.csproj

Tracing Individual Tool Calls

Every tool call gets a per-invocation correlation ID (a GUID). It's cheap to generate so it's always created, but it's only surfaced when you need it: it's included in every JSON error response (correlationId) and attached to that call's log lines via ILogger.BeginScope, so a user reporting a failure can hand you one ID that ties back to the full server-side log entry — without needing to grep timestamps.

For deeper, opt-in tracing of each tool invocation (start/stop, duration, success/failure) as a System.Diagnostics.Activity span, set RoselineMCP:EnableDiagnosticLogging to true (it's already true in appsettings.Development.json):

ROSELINE_RoselineMCP__EnableDiagnosticLogging=true dotnet run --project RoselineMCP/RoselineMCP.csproj

This uses the built-in ActivitySource/Activity APIs rather than the OpenTelemetry SDK, so it adds no extra dependency. Spans are logged exclusively through the existing ILogger pipeline, which is already routed to stderr — never to stdout (the MCP JSON-RPC channel) — and nothing is ever sent over the network; when the flag is off (the default), no listener is registered and the spans cost essentially nothing.

Roadmap

Additional analyzer rule sets (SonarAnalyzer, FxCop)
Auto-fix suggestions with confidence scoring
CI/CD integration for automated analysis pipelines
Multi-solution support in a single session
Incremental analysis (only changed files)
Custom analyzer rule configuration via MCP

Want to contribute? Pick any roadmap item and open a PR!

Documentation

Documentation site -- overview, tool reference, and the token-savings benchmark (built from website/, deployed to GitHub Pages)
docs/API.md -- Full request/response reference for every MCP tool, service interfaces, models, and the error-response contract
docs/AGENT-BENCHMARK.md -- End-to-end A/B: does an AI agent actually spend fewer tokens with RoselineMCP? (honest answer — a large-codebase win, break-even on small)
docs/ARCHITECTURE.md -- Layered architecture, data flow, and design patterns
PROMPTS.md -- Example prompts and end-to-end workflows for each tool
CHANGELOG.md -- Release history and breaking changes
SECURITY.md -- Vulnerability reporting and the MSBuild code-execution caveat
CONTRIBUTING.md -- Development setup and PR process

Contributing

Contributions are welcome! Please read CONTRIBUTING.md first.

Fork the repository
Create your feature branch (git checkout -b feature/amazing-feature)
Commit using conventional commits (git commit -m 'feat: add amazing feature')
Push to the branch (git push origin feature/amazing-feature)
Open a Pull Request

License

Acknowledgments

Built on Roslyn -- The .NET Compiler Platform
Powered by Roslynator -- C# analyzers and refactorings
Uses DiffPlex -- Diff generation library
Implements Model Context Protocol -- AI assistant integration protocol

Built with care by Atypical Consulting -- opinionated, production-grade open source.

RoselineMCP

README

RoselineMCP

Table of Contents

Why RoselineMCP

Quick Start

Features

Tech Stack

Getting Started

Prerequisites

Installation

Claude Desktop configuration (NuGet global tool)

Claude Desktop configuration (Docker)

Claude Desktop configuration (build from source)

MCP Client Compatibility

Available Tools

1. AnalyzeSolution

2. ListDiagnostics

3. ApplyFixes

4. CreatePatch

Code Navigation Tools (read-only)

5. SearchSymbols

6. GetSymbolInfo

7. FindReferences

8. FindImplementations

9. GetCallGraph

10. GetTypeHierarchy

13. GetSymbolAtPosition

Code Editing Tools (preview by default)

11. EditMember

12. RenameSymbol

Tool Annotations

Tool Compatibility Policy

Supported Analyzers

Examples

Analyzing a Solution

Applying Fixes

Configuration

Environment Variables

appsettings.json

Architecture

Project Structure

Performance

Security

Troubleshooting

Common Issues

Debug Logging

Tracing Individual Tool Calls

Roadmap

Documentation

Contributing

License

Acknowledgments

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