Myelin: MD Extractor and Evaluator for Claude Code Procedural Memory

Myelin: MD Extractor and Evaluator for Claude Code

Myelin is a tool that addresses two specific problems developers face when working with Claude Code and procedural memory files: manually writing .md procedure files after successful sessions, and lacking visibility into whether Claude actually follows those procedures.

Core Features

The tool operates through three main functions:

• Extraction: When a session succeeds with no existing procedure, Myelin extracts a .md file from the trace. You review, approve or edit it, eliminating the need to hand-write procedures from memory.
• Observability: When a session follows an existing procedure, Myelin tracks step-by-step what Claude actually did, categorizing actions as Followed, Skipped, or Diverged. Across sessions, patterns emerge, and Myelin suggests diffs.
• Evaluation: Every session receives a verdict: Success, Partial, or Failure. This provides actual success rates per procedure rather than relying on gut feeling.

Technical Implementation

Myelin hooks into Claude Code via PostToolUse and captures every tool call. The output is plain .md files that can be downloaded and kept in your repository, or left in Myelin where it serves the right procedure via search when matching tasks come up.

Setup and Access

Setup requires just an MCP server plus one hook in settings.json. The tool offers a free tier with 50 sessions/month.

Resources

• SDK: https://github.com/yahnyshc/myelin-sdk
• Site: https://myelin.vercel.app
• HN Discussion: https://news.ycombinator.com/item?id=47545239

This tool is particularly useful for developers who use Claude Code for deployment, running migrations, handling tickets, and other procedural tasks where maintaining accurate documentation and verifying execution is important.