Table of Contents
Give Codex a persistent, self-evolving toolkit. Add microfn as an MCP server and Codex can create custom functions, update them as needs change, and build a reusable library—all deployed instantly to a secure sandbox.
Build tools once, then refine them. Every function persists across sessions, ready to be patched, composed, and evolved.
1. Edit configuration
Open ~/.codex/config.toml in your preferred editor. If it doesn’t exist, you can create it.
2. Add microfn server
Add the following [mcp_servers.microfn] block to the file:
[mcp_servers.microfn]command = "npx"args = ["-y", "mcp-remote", "https://mcp.microfn.dev/mcp"]3. Authenticate
When you first run a command using the microfn server, you will be prompted to authenticate via OAuth in your browser.
Read more
For more details on available tools and advanced configuration, check out the microfn MCP documentation.
Built with microfn, your toolbox for composable functions
Microfn is a tiny cloud runner for composable JavaScript functions. Write your function, hit save, and microfn deploys it instantly.