Simple markdown files definitely work, but the downside is that they only hold what you actually remember to write down / tell your agents to write down. The useful learnings are usually in the session itself i.e. the 3 approaches the agent tried before one of them worked.

Beacon keeps the full execution trace (prompts, reasoning, tool calls, commands) outside the agent's context and distills lessons from it. Ultimately the agent still only has access to snippets of information (via skill progressive disclousure) but it's drawn from much richer session data rather than what you remembered to note down. Also you don't have to maintain it yourself!

A markdown file works well as long as you don't use a second agent / tool that needs access to this same file. Otherwise, you will find that the copies of the file drift apart.

It's better to store the memory outside of all tools and then connect all of them to it via MCP. Then you have a single store where all of the tools can read from and write to.

This is one of the ideas we used when building up memory in Substrate. How many tools are using this file as memory?

I did too: "keep an obsidian vault of things you need to remember. make a skill for it"

I don't even know how obsidian works.

And I use a harness where the agents can easily look up & search other sessions, or past sessions.