MCP tool select/filter/group
What feature would you like to see?
User active selection:
As codex user, I want to be able to actively select the MCP tools (in codex CLI/vscode extension) and choose to enable/disable them for my current workflow to avoid too many MCP tools fill up the context window / distract LLM.
Passive grouping/filtering:
This could be useful when user configured many MCP servers, but didn't actively select servers/tools they need, so fitting all tool descriptions consumes tokens & distracts LLM.
Might provide some inspirations:
Approach by copilot: https://github.blog/ai-and-ml/github-copilot/how-were-making-github-copilot-smarter-with-fewer-tools/
Approach by Cursor (Tool Search Tool): https://www.anthropic.com/engineering/advanced-tool-use
Additional information
Some relevant PRs didn't seem to go through:
https://github.com/openai/codex/pull/3255
https://github.com/openai/codex/pull/4835
3 Comments
This is a real need across the MCP ecosystem, not just Codex.
For context on why filtering matters: each MCP tool schema costs 550-1,400 tokens. With 50+ tools loaded, that's 30K+ tokens consumed before any user input. The problem scales linearly with tool count.
I built mcp-checkup to measure exactly this — it gives per-tool token costs and A-F grades so you can see which tools are worth the context budget:
Having data on per-tool costs makes it much easier to decide which tools belong in which groups/filters.
Dealing with this exact token bloat was driving me crazy, so I built toolc. It’s a middleware gateway that bundles multiple MCP and OpenAPI servers into one compact surface. Basically, it hides the massive raw catalog from the agent and only exposes a strict subset you configure. Great for local setups if you're tired of paying the "tool tax" on every prompt.
Repo: https://github.com/aak204/Tool-Catalog-Compiler
MCP allow/deny lists and lazy discovery implement filtering.