Agent skills

Agent Plugins 1.0 says plugin.json at the root and mcp.json beside it. Claude Code 2.1.x wants .claude-plugin/plugin.json and .mcp.json. Here is what each client actually loads, tested against a real plugin, and the dual-layout directory that satisfies both.

Cursor did not delete rules. It split them. This checklist sorts a .cursorrules file and a folder of .mdc rules into the four things they should be in Cursor 3.11: an AGENTS.md, a small set of surviving rules, skills, and subagents, then bundles the result as a plugin.

Visual Studio 2026 18.8 puts expert-authored .NET and Azure agent skills in the tool picker under a Built-in category, disabled by default. The default is the interesting part.

On 2026-07-31 Microsoft shipped a polyglot unit-test agent in dotnet/skills. The interesting part is the mandatory pre-completion gate that pseudo-mutates your assertions before the agent is allowed to say it is done.

Agent skills and MCP servers in GitHub Copilot code review went GA on 2026-07-29. Here is where the files live, why skills load from the head branch, and why every MCP tool call in a review is read-only.

How to convert .github/prompts/*.prompt.md into .github/skills/<name>/SKILL.md so GitHub Copilot loads them automatically. What breaks, what maps 1:1, and how to verify each skill fires.

There is no single Skill type in the Microsoft Agent Framework, but you can package domain expertise as a reusable agent, reuse it in-process with AsAIFunction, and advertise it across frameworks as an A2A AgentSkill. Full walkthrough on Agent Framework 1.0 and .NET 11.

Build a skill to change how Claude works, a subagent to protect your context window, and an MCP server to reach a system Claude cannot otherwise touch. They solve three different problems, not one. Here is the decision, the mechanics, and the config for each.

Copilot Chat reads your .github/copilot-instructions.md fine, but Agent mode and *.instructions.md files often look ignored. Here is the actual checklist: settings, file locations, applyTo globs, and how to prove the file made it into context.

A 2026 walkthrough for wiring RAG into Claude Code 2.1.x: when agentic grep stops scaling, how to attach a hybrid BM25 + dense vector MCP server, how to wrap a retrieval CLI in a custom skill, and how Anthropic's contextual embeddings technique pushes recall above 92%. Anchored to claude-sonnet-4-6, claude-opus-4-7, and Claude Context 0.x.