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CLI vs MCP (IBM Technology)

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CLI vs MCP (IBM Technology)

Martin Keen (IBM) gives a more nuanced take on the CLI-vs-MCP debate than the partisan version in Printing Press (Nate Herk video). Conclusion: use both — CLI when commands map to the job, MCP when abstraction or governance justifies the cost.

Key claims

  • CLI argument (echoes Printing Press): models trained on millions of CLI examples (Stack Overflow, man pages). Don't need a schema for grep -n or git log. MCP injects every tool's schema into context at session start — a few thousand tokens before the agent does anything.
  • GitHub MCP server example: 80 tools, ~55,000 tokens of definitions injected on every session, even if you only need 1–2.
  • CLI fails when the raw tool doesn't return what you need. Demo: fetching modelcontextprotocol.io (a Next.js SPA).
    • MCP Fetcher (headless browser): single tool call, ~250 tokens, a few seconds, works.
    • CLI curl approach: curl gets only the JS bundle (no rendered HTML). Agent then improvises — strips HTML, looks for embedded JSON, eventually writes a Python script to reverse-engineer Next.js's streaming format. Several minutes, 2,000+ tokens.
    • "If the agent ever starts reverse-engineering a JavaScript framework just to read a webpage, that's a good sign it picked the wrong one."
  • CLI wins when:
    • File ops, git, text processing, scripts
    • Knowledge already in training data
    • Composability via pipes (MCP tool calls are independent)
  • MCP wins when:
    • Raw tool gap is wide (rendered web pages, complex APIs)
    • Auth needed (OAuth tokens, channel IDs, refresh) — server manages it, agent just declares intent
    • Per-user access control + audit trails — built into the protocol; very hard to bolt onto CLI later. Critical for org-level deployment.
  • Verdict: not either/or. The best agents (and the user who prompts them) pick the right tool per job.

Cross-source resonance & contradictions

  • Important nuance against Printing Press (Nate Herk video)'s CLI > MCP > API tier list. The Printing Press argument is largely about single-user, local dev workflows. IBM's argument adds enterprise/auth/audit dimensions where MCP wins. Both can be right in their own scope.
  • Echoes Boris Cherny's "to the model, it's just tokens" view from Boris Cherny on Coding Is Solved (Sequoia AI Ascent) — Boris also says use whatever fits, MCP, CLI, computer use, doesn't matter.
  • Confirms the GitHub-MCP-bloat anecdote that's becoming canonical in this discourse.

Cross-links