roslyn-mcp-tools

roslyn-mcp-tools is a cursor rule for Cursor from VuDZ/RoslynMcpServer. It costs 512 tokens per session, scanned A, original, MIT.

A set of rules mapping Roslyn MCP tasks to the correct tools. Roslyn is Microsoft's technology for reading and analysing .NET source code, while MCP is a way for an agent to call external tools.

In plain words
What is it for?
Use it when choosing tools to inspect C# projects, find definitions or usages, examine libraries, rename projects, build, run, or test .NET code.
Why use it?
It prevents the agent from confusing source-file outlines, type information, decompiled library code, symbol searches, and build or test commands.

Cursor rule for Cursor

Written for Cursor: installed under .cursor/.

Good fit Use it when choosing tools to inspect C# projects, find definitions or usages, examine libraries, rename projects, build, run, or test .NET code.

Compare 6 cursor rules from other repositories ↓
Install with agentmods
npx agentmods add rules/vudz/roslynmcpserver/roslyn-mcp-tools
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Clone the repo
git clone --depth 1 https://github.com/VuDZ/RoslynMcpServer

Made for: Cursor.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for roslyn-mcp-tools

README.md
[![agentmods](https://agentmods.dev/badge/rules/vudz/roslynmcpserver/roslyn-mcp-tools/github.svg)](https://agentmods.dev/rules/vudz/roslynmcpserver/roslyn-mcp-tools)
Your own site
<a href="https://agentmods.dev/rules/vudz/roslynmcpserver/roslyn-mcp-tools"><img src="https://agentmods.dev/badge/rules/vudz/roslynmcpserver/roslyn-mcp-tools/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for roslyn-mcp-tools

Your own site · 80×15
<a href="https://agentmods.dev/rules/vudz/roslynmcpserver/roslyn-mcp-tools"><img src="https://agentmods.dev/badge/rules/vudz/roslynmcpserver/roslyn-mcp-tools.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 512 This file is loaded in full into every session.
When invoked 512 The same file — it is already loaded in full.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00512 $0.00512
Opus 5 $0.00256 $0.00256
Sonnet 5 $0.00102 $0.00102
Haiku 4.5 $0.00051 $0.00051

Measured 2d ago against content hash 1aa5eed59163, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-16, from the pricing page.

Security

Grade A, and why

roslyn-mcp-tools scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.cursor/rules/roslyn-mcp-tools.mdc · 33 lines

What it actually says

Tool mapping (avoid mixups)

Intent Tool Key args
File/folder skeleton (disk) get_code_skeleton path only (.cs or dir; max 20 files; skips bin/obj/Test)
Type skeleton in loaded workspace get_class_skeleton symbol / workspace context
External/NuGet type body decompile_type assemblyName or assemblyPath + fullTypeName
External signatures only get_decompiled_class_skeleton same assembly args
Method in decompiled type get_decompiled_method_body assembly + type + method
Explore DLL explore_assembly assemblyName or assemblyPath
Symbol find find_symbol_definition / find_usages / find_symbol_references prefer find_usages when only name known
Project folder rename rename_project SDK-style; dryRun first; no namespace chain
Interfaces/base find_implementations not find_usages
Plain text in .cs search_code or host Grep leftover branding → caseSensitive=true
Build / test / run run_dotnet_build / run_dotnet_test / run_specific_test / run_dotnet_run never shell dotnet for these; build: default noIncremental, optional configuration; tests: timeoutSeconds (build+test budget), optional noBuild/noRestore
NuGet vulns run_nuget_audit separate from compile errors
Git status for agents get_changed_files porcelain + suggested tests; no full diff

Failure UX

Missing path on get_code_skeleton → friendly text error (do not throw unhandled MCP exception). Do not accept assemblyName/typeName on file skeleton tools.

Hybrid search (AGENTS)

  • Shell grep/Select-String forbidden for agent workflow.
  • C# symbols → MCP after load_workspace.
  • Strings/comments/non-C# → host Grep/SemanticSearch OK.
Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 33 lines · 512 tokens per session scan A 1aa5eed59163

Subscribe to this mod's changes

roslyn-mcp-tools is a cursor rule published in the GitHub repository VuDZ/RoslynMcpServer (7 stars, last pushed yesterday), licensed MIT. It adds 512 tokens to every session, about $0.0026 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-14.