CLI over MCP: a small Chrome DevTools experiment in Copilot CLI

I ran the same browser smoke task through two paths: direct Chrome DevTools MCP and a custom CLI skill around mcp2cli . In GitHub Copilot CLI with gpt-5.3-codex-medium , direct Chrome DevTools MCP added about 5k tokens of upfront context before the agent did any work. The runtime table is too small and too noisy to rank the tools. The useful question is where the agent pays to discover the browser-control surface. mcp2cli README says it can “Save 96-99% of the tokens wasted on tool schemas every turn.” That is a strong claim and frankly I didn't no expect that sort of numbers... It's just the CLI part resonates with me - (a) there's no system prompt pollution with CLI, (b) if you choose between gh CLI and GitHub MCP the former would be better due to the fact that model already knows the tool and there's less tokens wasted on JSON schemas and tool calls. I used Chrome DevTools MCP a lot and I have chosen this MCP as a test bed to try mcp2cli . This came handy cause I started my experiments with the minimal pi coding agent and it doesn't bundle any MCP integration, just the basic bash tool, I was very much happy not to bloat my instal with a dedicated MCP plugin. Although in this cases I cmpared MCP vs CLI using a fully fledged GitHub CLI. Tool discovery is part of the experiment. Native MCP gives the agent a tool surface by loading schemas into context. A CLI wrapper makes the agent discover the surface the way it discovers any other command-line tool: list, search, ask for help, run a small probe, write down what worked. That changes where the discovery cost lands. The Setup I ran this in GitHub Copilot CLI using gpt-5.3-codex-medium : Copilot stock MCP servers were disabled. The app under test was a private Pythobn/Streamlit codebase. The browser task was the same 9-step smoke test in both variants. One variant used direct Chrome DevTools MCP. Another variant used a custom skill that wraps Chrome DevTools MCP via mcp2cli . The custom skill itself started as an ad-h