[mksglu]

Right, context-mode doesn't change how MCP tool definitions get loaded into context. That's the "input side" problem that Cloudflare's Code Mode tackles by compressing tool schemas. Context-mode handles the "output side," the data that comes back from tool calls. That said, if you're writing your own MCPs, you could apply the same pattern directly. Instead of returning raw payloads, have your MCP server return a compact summary and store the full output somewhere queryable. Context-mode just generalizes that so you don't have to rebuild it per server.

[re5i5tor]

Hmmm. I was talking about the output side. When data comes back from an MCP tool call, context-mode is still not in the loop, not able to help, is it?

Edit: clarify "MCP tool"

[re5i5tor]

I dug into this further. Tested empirically and read the code.

Confirmed: context-mode cannot intercept MCP tool responses. The PreToolUse hook (hooks/pretooluse.sh) matches only Bash|Read|Grep|Glob|WebFetch|WebSearch|Task. When I called my obsidian MCP's obsidian_list via MCP, the response went straight into context — zero entries in context-mode's FTS5 database. The web fetches from the same session were all indexed.

The context-mode skill (SKILL.md) actually acknowledges this at lines 71-77 with an "after-the-fact" decision tree for MCP output: if it's already in context, use it directly; if you need to search it again, save to file then index. But that's damage control — the context is already consumed. You can't un-eat those tokens.

The architectural reason: MCP tool responses flow via JSON-RPC directly to the model. There's no PostToolUse hook in Claude Code that could modify or compress a response before it enters context. And you can't call MCP tools from inside a subprocess, so the "run it in a sandbox" pattern doesn't apply.

So the 98% savings are real but scoped to built-in tools and CLI wrappers (curl, gh, kubectl, etc.) — anything replicable in a subprocess. For third-party MCP tools with unique capabilities (Excalidraw rendering, calendar APIs, Obsidian vault access), the MCP author has to apply context-mode's concepts server-side: return compact summaries, store full output queryably, expose drill-down tools. Which is essentially what you suggested above.

Still very high value for the built-in tool side. Just want the boundary to be clear.

Correct any misconceptions please!