Maybe https://context7.com/leanprover/lean4 is what you're looking for? I am not familiar with Lean 4 but Context7 has been working well enough for me, working in a completely different field though.
For OP: Zig is also on Context7.
For OP: Zig is also on Context7.
But context7 returns semantically processed responses that often summarize or rephrase the information instead of quoting it. And that's why there is now zig-mcp which returns documentation in markdown format for stdlib and builtin functions