dotnet

Coding rules for developing an MCP server in a .NET codebase. They guide documentation, file organization, naming, validation, and code structure for AI-assisted work.

In plain words
What is it for?
Use them when writing or changing .NET MCP server code, especially public APIs, larger classes, and cross-cutting components.
Why use it?
They make unfamiliar .NET code easier for an AI agent to understand and modify consistently.

Cursor rule for Cursor

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.

agentmods
npx agentmods add rules/willibrandon/netcontextserver/dotnet
Clone the repo
git clone --depth 1 https://github.com/willibrandon/NetContextServer

Made for: Cursor.

Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 606 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00000 $0.00606
Opus 5 $0.00000 $0.00303
Sonnet 5 $0.00000 $0.00121
Haiku 4.5 $0.00000 $0.00061

Measured yesterday against content hash 1dc7f659790e, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

dotnet 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 yesterday.

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/dotnet.mdc · 69 lines

How it starts

The opening of the file, as written. The whole thing — 69 lines — stays where its author put it; the contents beside it link to each section on GitHub.

.NET Codebase Context MCP Server Development Rules

This rule applies to all .NET code files in the project and provides guidance for implementing the MCP server with specific optimizations for Claude 3.7 Sonnet integration.

Code Documentation for AI Assistance

  • Include comprehensive XML documentation for all public and protected members
  • Add code examples within XML comments for complex functionality
  • Document "why" behind implementation decisions, not just "what" the code does
  • Use consistent terminology across all documentation
  • Include parameter validation logic in method documentation
  • Specify explicit return value descriptions and possible exceptions
  • Add class/interface relationship diagrams in code comments for complex hierarchies

Code Organization

  • Keep files under 300 lines when possible for better AI comprehension
  • Use partial classes to logically organize larger components
  • Follow consistent naming conventions for related patterns
  • Group related functionality into clearly named namespaces
  • Create dedicated classes for cross-cutting concerns
  • Use explicit rather than implicit patterns to improve AI code understanding
  • Prefer composition over inheritance for better AI reasoning

Implementation Guidelines

  • Prioritize readability over clever or overly compact code
  • Implement one complete feature at a time
  • Use strongly typed models for all data exchanges
  • Create dedicated DTOs for MCP protocol interactions
  • Add comprehensive input validation with descriptive error messages
  • Implement self-explanatory function and variable names
  • Avoid magic numbers and strings; use constants with descriptive names

Testing Guidelines

  • Write unit tests for all public APIs with descriptive test names
  • Create integration tests for MCP protocol interactions
  • Add performance tests for critical path operations
  • Include contract tests for MCP protocol compliance
  • Cover edge cases and failure scenarios in tests
  • Document test coverage goals and gaps

Read the full file on GitHub · 69 lines

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. yesterday First seen · 69 lines · 606 tokens per session scan A 1dc7f659790e

Subscribe to this mod's changes

dotnet is a cursor rule published in the GitHub repository willibrandon/NetContextServer (32 stars, last pushed 1y ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 606 tokens. 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 2026-08-30.