dotnet-sherlock-mcp

Sherlock MCP for .NET

Sherlock MCP for .NET is a comprehensive Model Context Protocol (MCP) server that provides deep introspection capabilities for .NET assemblies. It enables Language Learning Models (LLMs) to analyze and understand your .NET code with precision, delivering accurate and context-aware responses for complex development scenarios.

This tool is essential for developers who want to harness LLM capabilities for:

• Deep codebase analysis - Understanding complex .NET architectures and dependencies
• Precise type information - Getting detailed metadata about types, members, and their signatures
• Automated documentation - Extracting and utilizing XML documentation and attributes
• Custom tooling - Building sophisticated tools that interact with .NET assemblies
• Code generation - Creating accurate code based on existing type structures

Key Features

• Comprehensive MCP Server: Provides 40 specialized tools for .NET assembly analysis, with an optional 20-tool core profile
• Advanced Assembly Introspection: Deep reflection-based analysis of types, members, and metadata
• Rich Member Analysis: Detailed inspection of methods, properties, fields, events, and constructors
• Smart Filtering & Pagination: Advanced filtering by name/attributes with efficient pagination for large datasets
• XML Documentation Integration: Automatic extraction of summary, parameters, returns, and remarks
• Performance Optimized: Caching, pagination, and memory-efficient processing
• Stable JSON API: Consistent envelopes with versioning and structured error codes
• .NET 9.0 Native: Built on the latest .NET platform with modern C# features
• Project Integration: Solution and project file analysis with dependency resolution
• Workflow Prompts: explore_package, explain_type and who_calls prompts give one-click entry points into common analysis workflows
• Current MCP SDK: Built on ModelContextProtocol 2.1.0 (GA)
• Current MCP Specification: Speaks protocol revision 2026-07-28, and negotiates down automatically for clients on earlier revisions

What's New in 2.14.0

• Claude Code plugin: /plugin marketplace add jcucci/dotnet-sherlock-mcp and /plugin install sherlock@dotnet-sherlock-mcp install the server plus a skill that teaches agents the Sherlock workflow. See Claude Code plugin.
• get_type_members and tool profiles: one paginated, filterable tool lists every member kind, and --profile core / SHERLOCK_TOOL_PROFILE=core trims the surface to the essential tools. The per-kind member tools are deprecated.
• Structured output and error guidance: the core browsing tools publish an outputSchema and return structuredContent, and failed calls carry isError: true with did-you-mean candidates and fix-it suggestions.
• Cancellation, progress and elicitation: long scans can be cancelled and report progress, and an ambiguous simple type name prompts the client to choose. See CHANGELOG.md for full details.

Installation

Run with dnx (.NET 10 SDK)

With the .NET 10 SDK, dnx downloads the package from NuGet and runs it directly — no install step:

dnx -v q --yes Sherlock.MCP.Server@2.14.0

--yes skips the interactive confirmation prompt, which an MCP client launching the server over stdio can't answer. -v q stops dnx from printing a "Skipping NuGet package signature verification." notice to stdout the first time it downloads a version, which would otherwise corrupt the MCP stream and fail that first connection. Both are dnx options, so they must come before the package id; anything after it is passed to the server. Pinning the version keeps launches reproducible; bump it when you want to upgrade. The package is published with the McpServer package type, so it is also listed as an MCP server on NuGet.org.

Install as a global tool

On any supported SDK (.NET 8 or later), install the global tool from NuGet (adds sherlock-mcp to your PATH):

dotnet tool install -g Sherlock.MCP.Server

Alternatively, during development you can run the server locally:

dotnet run --project src/server/Sherlock.MCP.Server.csproj

Configure Your MCP Client

Sherlock runs as a standard MCP server that communicates over stdio.

Claude Code plugin

This repository is also a Claude Code plugin marketplace. The sherlock plugin bundles the server (launched with dnx, so it needs the .NET 10 SDK) and a skill that teaches the agent the locate → orient → drill-in → relationships workflow:

/plugin marketplace add jcucci/dotnet-sherlock-mcp
/plugin install sherlock@dotnet-sherlock-mcp

The plugin starts the server with the core tool profile, which matches the tools the skill covers. To expose every tool, set SHERLOCK_TOOL_PROFILE=full in the environment Claude Code is launched from.

Each user runs these commands once; restart Claude Code (or run /reload-plugins) afterwards. To pick up a new release, run /plugin marketplace update dotnet-sherlock-mcp. If you previously registered Sherlock with claude mcp add, remove that entry (claude mcp remove sherlock) so the tools aren't loaded twice.

Team setup

To offer the plugin to everyone working in a repository, commit the following to that repository's .claude/settings.json. Claude Code prompts each teammate to install it when they trust the folder, so nobody has to type the commands above:

{
  "extraKnownMarketplaces": {
    "dotnet-sherlock-mcp": {
      "source": {
        "source": "github",
        "repo": "jcucci/dotnet-sherlock-mcp"
      }
    }
  },
  "enabledPlugins": {
    "sherlock@dotnet-sherlock-mcp": true
  }
}

Teammates still need the .NET 10 SDK on their PATH for dnx.

Using dnx

• Claude Code:

claude mcp add sherlock -- dnx -v q --yes Sherlock.MCP.Server@2.14.0

• VS Code (.vscode/mcp.json):

{
  "servers": {
    "sherlock": {
      "type": "stdio",
      "command": "dnx",
      "args": ["-v", "q", "--yes", "Sherlock.MCP.Server@2.14.0"]
    }
  }
}

Using the global tool

• Cursor: Settings → MCP / Custom tools → Add tool → Command: sherlock-mcp
• Claude Desktop / other MCP clients: Add a server entry pointing to the sherlock-mcp command. Example JSON entry (refer to your client’s docs for exact file location/format):

{
  "servers": {
    "sherlock": {
      "command": "sherlock-mcp"
    }
  }
}

No arguments are required. The server self-registers all tools when launched.

Tool profiles

Large tool lists cost agents context and discoverability (Claude Code switches to deferred Tool Search once tool descriptions grow past roughly 10% of the context window). Sherlock can start with a smaller surface:

Profile	Tools	Contents
full (default)	40	Every tool, including the deprecated per-kind member tools
core	20	Discovery (find_assembly_by_class_name, find_assembly_by_file_name, find_assembly_by_nuget_package, get_project_output_paths, open_assembly), orientation (get_assembly_info, get_types_from_assembly, get_type_info, get_type_hierarchy), members and docs (get_type_members, search_members, analyze_method, get_xml_docs_for_type, get_xml_docs_for_member) and relationships (find_implementations_of, find_methods_returning, find_extension_methods_for, find_references_to, get_method_calls) and decompilation (decompile_member)

Select a profile with the --profile argument or the SHERLOCK_TOOL_PROFILE environment variable (the argument wins). An unknown profile name stops the server with an error.

{
  "servers": {
    "sherlock": {
      "command": "sherlock-mcp",
      "args": ["--profile", "core"]
      // or: "env": { "SHERLOCK_TOOL_PROFILE": "core" }
    }
  }
}

Auto-Configure for .NET Projects

You usually don't need to paste anything. Sherlock ships its usage guidance in the MCP instructions field returned at initialize, and most MCP clients (including Claude Code) surface that to the agent automatically — so the guidance stays correct and versioned with the package, with no copy-paste to maintain.

The snippets below are optional reinforcement. Keep them short and principle-based rather than enumerating tool names and workflows: a static list pasted into your repo will drift as Sherlock's tools evolve, whereas the tools' own descriptions (and the server instructions) always match the version you're running.

Tool names are exposed in snake_case (get_type_members, search_members, …); argument names stay camelCase (projection, nameContains).

Claude Code (CLAUDE.md)

If you installed the Claude Code plugin, its skill already covers this. Otherwise, you can add a short, optional pointer to your project's CLAUDE.md:

## .NET Assembly Analysis

Use the Sherlock MCP tools (`get_type_members`, `search_members`, …) for .NET type/assembly
questions instead of guessing. Locate DLLs with the `find_assembly_by_*` / `get_project_output_paths`
tools rather than hardcoding bin paths. Start lean — `search_members` or `get_types_from_assembly`,
then drill in — and pass `projection='full'` only when you need parameters/attributes/modifiers.
The tools' own descriptions cover the specifics.

Cursor (.cursor/rules)

The single-file .cursorrules format is deprecated (and silently ignored in Cursor's Agent mode). Add a Project Rule at .cursor/rules/sherlock.mdc instead:

---
description: Use Sherlock MCP for .NET assembly/type analysis
alwaysApply: true
---

- Prefer the Sherlock MCP tools (snake_case, e.g. `get_type_members`, `search_members`) over guessing about .NET APIs.
- Find DLLs with `find_assembly_by_*` / `get_project_output_paths`; don't hardcode `bin/Debug/<tfm>/*.dll`.
- Start lean (`search_members` / `get_types_from_assembly`); request `projection='full'` only when you need parameters/attributes/modifiers.

Other agents (AGENTS.md)

For tools that follow the cross-editor AGENTS.md convention, the same short pointer works — drop the Claude Code snippet above into your AGENTS.md.

Global configuration

For system-wide usage, add to your global agent settings:

For .NET work, use the Sherlock MCP tools (snake_case) to analyze assemblies, types, and members instead of guessing. Start lean and opt into projection='full' only when you need detail.

How To Prompt It

Below are compact prompt snippets you can paste into your chat to get productive fast. Adjust paths to your local DLLs.

General setup

You have access to an MCP server named "sherlock" that can analyze .NET assemblies. Prefer these tools for .NET questions and include short reasoning for which tool you chose. Ask me for the assembly path if missing.

Enumerate members for a type

Analyze: /absolute/path/to/MyLib/bin/Debug/net9.0/MyLib.dll
Type: MyNamespace.MyType
List methods, including non-public, filter name contains "Async", include attributes, return JSON.

Get XML docs for a member

Use GetXmlDocsForMember on /abs/path/MyLib.dll, type MyNamespace.MyType, member TryParse. Summarize the summary + params.

Find types and drill in

List types from /abs/path/MyLib.dll; then get type info for the first result and list its nested types.

Tune paging and filters

Use GetTypeMembers on /abs/path/MyLib.dll, type MyNamespace.MyType, kinds method, sortBy name, sortOrder asc, skip 0, take 25, hasAttributeContains Obsolete.

Browse lean, then get detail (projection)

On /abs/path/MyLib.dll, run GetTypeMembers for MyNamespace.MyType with the default summary projection to see signatures. Then re-call GetTypeMembers with kinds method, nameContains and projection='full' only for the methods I name to get their parameters and attributes.

Trace relationships and call sites

On /abs/path/MyLib.dll: FindImplementationsOf MyNamespace.IMyService. Then FindReferencesTo that interface with analysisDepth='il' to find callers, and GetMethodCalls on the most relevant method to see what it invokes.

Tools Overview

Tool names: MCP clients call these tools in snake_case — GetTypeMembers → get_type_members, SearchMembers → search_members, and so on. The PascalCase names used throughout this README match the underlying C# methods and the tool descriptions your client displays.

Assembly Discovery & Analysis

• OpenAssembly: Returns a short asm_… handle to pass as assemblyHandle instead of assemblyPath on any tool that takes an assembly. The handle carries additionalAssemblies too, persists across server restarts (in handles.json under SHERLOCK_STATE_DIR, default the user's local app-data sherlock folder) and is pinned to the current build: after a rebuild, calls fail with StaleAssemblyHandle until it is reopened
• AnalyzeAssembly: Complete assembly overview with public types and metadata
• GetAssemblyInfo: Assembly-level metadata — identity/version, target framework, and referenced assemblies (projection=full adds all assembly attributes)
• FindAssemblyByClassName: Locate assemblies declaring a public type by simple, full or nested name; skips obj/, ref/, refint/, node_modules/, packages/, TestResults/ and dot-directories, and ranks bin/ matches first
• FindAssemblyByFileName: Find assemblies by file name under a root directory, with the same exclusions and ranking
• FindAssemblyByNugetPackage: Resolve a DLL from the local NuGet cache by package id (optional version/tfm)

Type Introspection

• GetTypesFromAssembly: List all public types with metadata (paginated)
• AnalyzeType (deprecated): Type metadata plus all members; use GetTypeInfo + GetTypeMembers projection=full
• GetTypeInfo: Detailed type metadata (accessibility, generics, nested types)
• GetTypeHierarchy: Inheritance chain and interface implementations
• GetGenericTypeInfo: Generic parameters, arguments, and variance information
• GetTypeAttributes: Custom attributes declared on types
• GetNestedTypes: Nested type declarations

Member Analysis (Filterable & Paginated)

• GetTypeMembers: Methods, properties, fields, events and constructors of a type in one paginated list. Narrow with kinds (method|property|field|event|constructor), nameContains and hasAttributeContains; summary items are { kind, name, signature }, projection=full adds each kind's structured fields
• AnalyzeMethod: Deep method analysis with overloads and attributes
• Deprecated, kept for a release or two: GetTypeMethods, GetTypeProperties, GetTypeFields, GetTypeEvents, GetTypeConstructors (use GetTypeMembers with kinds) and GetAllTypeMembers (use GetTypeMembers projection=full)

Member Search

• SearchMembers: Search a whole assembly for members whose name contains a fragment — the entry point when you know a member name but not its declaring type. Filter by memberKinds (method|property|field|event|type).

Reverse Lookup

• FindImplementationsOf: Types implementing an interface or deriving from a base class (open-generic match supported)
• FindMethodsReturning: Methods whose return type matches a given type (open-generic match supported)
• FindExtensionMethodsFor: Extension methods that extend a given type (scans static classes by this-parameter)
• FindReferencesTo: Broader sweep across parameters, fields, properties, events, and generic arguments; pass analysisDepth='il' to also resolve inbound callers from method bodies

IL Analysis

• GetMethodCalls: Read a method's IL body to list what it calls and which fields it touches — the "what does this method do?" question signature-level tools can't answer (aggregates across overloads; use .ctor/.cctor for constructors)

Decompilation

• DecompileMember: Decompile one member (method, property, field, event or constructor) to C# with ICSharpCode.Decompiler. Returns every overload of the name, or one overload when parameterTypes is given (e.g. string,int; an empty string selects the parameterless overload). Use .ctor/.cctor for constructors
• DecompileType: Decompile a whole type to C#. Not in the core profile; prefer DecompileMember

Both tools page their source by line: maxLines (default 400, max 5000) caps the page size, a page also stops early once it reaches about 90,000 characters so it always fits the response limit, and each page reports startLine, lineCount, totalLines, truncated and a continuationToken for the next page. Lines over 2,000 characters are clipped with a /* … more characters clipped */ marker and counted in clippedLines. Pass additionalAssemblies (or use an assemblyHandle opened with them) when dependencies live outside the assembly's folder; their folders are searched when resolving referenced types and their file stamps are part of the cache key. The full decompilation is cached by file stamp, so later pages are cheap. A type the assembly only forwards (e.g. System.String in a System.Runtime.dll facade) returns TypeForwarded with the defining assembly in recommendedParams.

Attributes & Metadata

• GetMemberAttributes: Attributes for specific members
• GetParameterAttributes: Parameter-level attribute information

XML Documentation

• GetXmlDocsForType: Extract type-level XML documentation
• GetXmlDocsForMember: Member-specific documentation (summary/params/returns/remarks)

Project & Solution Analysis

• AnalyzeSolution: Parse .sln files and enumerate projects
• AnalyzeProject: Project metadata, references, and build configuration
• GetProjectOutputPaths: Resolve output directories for different configurations
• ResolvePackageReferences: Map NuGet packages to cached assemblies
• FindDepsJsonDependencies: Parse deps.json for runtime dependencies

Configuration & Runtime

• GetRuntimeOptions: Current server configuration and defaults
• UpdateRuntimeOptions: Modify pagination, caching, and search behavior

Resources

Three resource templates let clients fetch a single type, doc entry or cached package without another tool call. Every variable is percent-encoded.

• sherlock://assembly/{path}/type/{fullName}: Type metadata, the same payload as get_type_info
• sherlock://assembly/{path}/docs/{memberId}: XML documentation for a documentation id such as T:Ns.Type or M:Ns.Type.Method(System.String)
• sherlock://nuget/{packageId}/{version}: The assembly a cached NuGet package version resolves to, the same payload as find_assembly_by_nuget_package

search_members, get_types_from_assembly and the find_* reverse-lookup tools return a resource_link to the type resource for each distinct type on the page, after the JSON text block. resources/read carries private caching hints; a URI whose assembly, type, doc id or package doesn't exist fails with -32602.

Template variables support completion/complete, returning at most 100 values:

• path: recently loaded assemblies, then .dll/.exe files and subfolders of the folder being typed
• fullName: type names (metadata form, e.g. List`1) from the assembly in the path context argument
• memberId: documentation ids from the XML file next to the path assembly
• packageId / version: package folders and their versions (newest first) in the local NuGet cache

Prompts

Three prompts encode common tool sequences as one-click entry points (Claude Code lists them as /mcp__sherlock__<name> slash commands). Each returns a single user message that walks the agent through the tools; they only call tools in the core profile, so they work under either profile.

• explore_package (packageId, version?): Resolves the package from the local NuGet cache (highest cached version when version is omitted), orients on the assembly, and summarizes its main types and entry points
• explain_type (assemblyPath, typeName): Hierarchy, members, XML docs and usages of one type
• who_calls (assemblyPath, typeName, memberName, additionalAssemblies?): Inbound callers of a member from IL, optionally across a comma-separated list of other assemblies

assemblyPath, typeName (with assemblyPath in the completion context), packageId and version (with packageId in the context) support completion/complete the same way as the resource template variables. prompts/list carries the same public caching hints as tools/list.

Advanced Filtering & Pagination

All member analysis tools support comprehensive filtering and pagination:

Filtering Options:

• caseSensitive (bool): Case-sensitive type/member matching
• nameContains (string): Filter by member name substring
• hasAttributeContains (string): Filter by attribute type substring
• includePublic / includeNonPublic (bool): Visibility filtering
• includeStatic / includeInstance (bool): Member type filtering

Pagination:

• skip / take (int): Standard offset pagination
• maxItems (int): Maximum results per request (default 50; FindReferencesTo defaults to 25)
• continuationToken (string): Token-based pagination for large datasets
• sortBy / sortOrder (string): Sort by name/access in asc/desc order

Response Shape (token efficiency)

Most enumerating tools default to a lean summary projection and let you opt into the heavier full payload only when you need it. Reach for full deliberately — summary is usually enough to decide your next call.

• projection (summary | full): supported by GetTypesFromAssembly, GetTypeMembers, GetTypeMethods, GetAssemblyInfo, GetMethodCalls, FindImplementationsOf, FindMethodsReturning, FindExtensionMethodsFor, and FindReferencesTo. summary returns just enough to browse (e.g. { kind, name, signature } for members); full adds structured fields (parameters, attributes, return type, modifiers, etc.). Note: the deprecated GetTypeProperties/Fields/Events/Constructors have a single fixed shape and take no projection.
• analysisDepth (signatures | il): FindReferencesTo only. signatures (default) scans member declarations; il additionally scans method bodies for inbound callers (slower).
• additionalAssemblies (string[]): widen the search scope for GetTypeHierarchy and the reverse-lookup tools. GetTypeHierarchy.derivedTypes stays null until you pass this.
• noCache (bool): bypass the response cache for a single call when you suspect stale results. Every tool that reads an assembly or project caches its response, keyed by the file stamps of its inputs (the assembly and any additionalAssemblies, the XML doc file beside it, or the project file and obj/project.assets.json), so a rebuild or restore invalidates it automatically. The find_assembly_by_* lookups and resolve_package_references (which read the shared NuGet package cache), configuration and handle tools are not cached. Two cases the stamps don't catch, where noCache=true is the fix: a dependency DLL dropped in beside an assembly that previously resolved only partially (keys stamp the assembly, not its siblings), and a restore for a project whose project.assets.json lives outside obj/ (e.g. UseArtifactsOutput or a custom BaseIntermediateOutputPath).
• assemblyHandle (string): accepted by every tool that takes assemblyPath, as an alternative to it (pass one, not both). Get one from open_assembly; it also supplies the additionalAssemblies it was opened with, and any you pass explicitly are added to them.

Type Resolution:

• Supports full names (Namespace.Type), simple names (Type), and nested types (Outer+Inner)
• Case sensitivity controlled by caseSensitive parameter
• Automatic fallback resolution for ambiguous type names

Response Schema

All tools return a stable JSON envelope:

{ "kind": "type.list|member.methods|...", "version": "1.0.0", "data": { /* result */ } }

The envelope is serialized as compact (unindented) JSON in the tool's text content block. The core browsing tools also advertise an MCP outputSchema and return the same envelope as structuredContent, so clients can validate and consume results without parsing text: search_members, get_types_from_assembly, get_type_info, get_type_members, get_type_methods, get_assembly_info, get_method_calls, decompile_member, find_implementations_of, find_methods_returning, find_extension_methods_for and find_references_to. Their schemas describe the default summary projection; projection='full' items add fields on top of it. Error results never carry structuredContent.

Error results are flagged with MCP's isError: true, so clients can tell a failure from a result without parsing the text. Errors use a consistent shape. Every error carries kind, version, code, and message; some add details, and guided errors add a suggestion, alternativeTools, or recommendedParams to point the agent at a next step:

{
  "kind": "error",
  "version": "1.0.0",
  "code": "MethodNotFound",
  "message": "No method named 'Parse' was found on type 'MyApp.Config' in MyApp.dll.",
  "suggestion": "Verify the type and method names. Use get_type_members with kinds=method to list available methods, or set includeNonPublic=true for private methods.",
  "alternativeTools": ["get_type_members", "analyze_method"]
}

Error codes:

• Not found: AssemblyNotFound (recommendedParams.similarFiles lists near-miss assemblies in the same folder), TypeNotFound / MemberNotFound (recommendedParams.candidates lists the closest names), MethodNotFound, PackageNotFound, VersionNotFound, XmlNotFound, ProjectNotFound, FileNotFound
• Bad input: AmbiguousTypeName (only for clients that can't elicit; recommendedParams.candidates lists the matching full names), InvalidArgument, InvalidProjection, InvalidAnalysisDepth, InvalidContinuationToken
• Loading: InvalidAssembly (not a managed assembly), DependencyNotFound (a referenced assembly couldn't be loaded), DependencyResolutionFailed, AccessDenied
• Limits & internal: ResponseTooLarge, InternalError

Roadmap

Shipped features and planned work are summarized in src/docs/roadmap.md; the live checklist is tracked in #87.

Contributing

Contributions are welcome. This repo includes an .editorconfig with modern C# preferences (file-scoped namespaces, expression-bodied members, 4-space indentation).

Commit Message Format

This project uses Conventional Commits for automated changelog generation. All commits must follow this format:

type(scope): description

Valid types:

• feat - A new feature
• fix - A bug fix
• docs - Documentation only changes
• style - Code style changes (formatting, semicolons, etc)
• refactor - Code change that neither fixes a bug nor adds a feature
• perf - Performance improvement
• test - Adding or correcting tests
• build - Changes to build system or dependencies
• ci - Changes to CI configuration
• chore - Other changes that don't modify src or test files
• revert - Reverts a previous commit

Examples:

git commit -m "feat(tools): add new assembly analysis tool"
git commit -m "fix: resolve null reference in type loader"
git commit -m "docs(readme): update installation instructions"

Development Setup

# Restore .NET tools (versionize, husky)
dotnet tool restore

# Install git hooks for commit validation
dotnet husky install

Guidelines

• Keep changes small and focused; add unit tests for new behavior.
• Follow the response envelope and error code conventions when adding tools.
• Run dotnet build and dotnet test locally before opening a PR.

Creating a Release

Maintainers can create releases using:

# Restore tools if not already done
dotnet tool restore

# Preview what will change
dotnet versionize --dry-run

# Create release (bumps version, updates changelog, creates git tag)
dotnet versionize

# Push changes and tag to trigger release workflow
git push --follow-tags

versionize only bumps the project version. Before pushing, bump both version fields in server.json, the Claude Code plugin's version in plugins/sherlock/.claude-plugin/plugin.json and .claude-plugin/marketplace.json, and the pinned dnx version in plugins/sherlock/.mcp.json (and in this README) in the same release commit, then re-point the tag at it. server.json is packed into the NuGet package as .mcp/server.json.

The release workflow will automatically:

1. Verify that the tag, server.json, the project version and the Claude Code plugin versions all match
2. Build and test the project
3. Create a GitHub Release with changelog notes
4. Publish the NuGet package and the MCP Registry entry

MCP Registry

mcp-name: io.github.jcucci/dotnet-sherlock-mcp

License

Sherlock MCP for .NET is licensed under the MIT License.