docs: explicitly forbid grepping rust source for mcp schemas and instruct usage of local json cache

nvim-core/src/instructions.md

@@ -29,3 +29,6 @@ If you need to access *any* Neovim API that does not have a dedicated tool (e.g.
 
 ## 3. The "Unix is NOT King" Rule
 You should **ALWAYS prioritize Neovim tools over basic unix terminal utilities** (like `cat`, `grep`, `sed`, `awk`, or PowerShell equivalents) for file read/writes and search/replace. If an interactive Neovim session is not currently open, the server will automatically spawn a persistent headless Neovim daemon in the background to execute your commands. Use Neovim as your primary AST-aware interface to the codebase at all times.
+
+## 4. Tool Schema Discovery
+Do **NOT** grep or search the Rust source code to find tool schemas or arguments. All lazy-loaded MCP tool schemas are automatically cached as JSON files on your disk. To understand a tool`s arguments, directly read `~/.gemini/antigravity-cli/mcp/win-nvim/<tool_name>.json` (or linux-nvim), or simply guess the arguments if it is a basic tool like `nvim_open_file` (e.g., `{"file": "/path/to/file"}`).