# lean-ctx — Token Optimization
lean-ctx is configured as an MCP server. Always use nebu-ctx MCP tools instead of built-in tools:
- Read files → `ctx_read(path, mode)` instead of built-in Read
- Shell commands → `ctx_shell(command)` instead of built-in Shell
- Search code → `ctx_search(pattern, path)` instead of built-in Grep
- List directories → `ctx_tree(path, depth)` instead of ls/find
ctx_read modes: auto, full, map, signatures, diff, task, reference, aggressive, entropy, lines:N-M.
Preferred workflow control: `ctx_workflow` (state + evidence + tool gating).
Fallback only if MCP is unavailable: prefix with `lean-ctx -c`:
- `lean-ctx -c git status`
- `lean-ctx -c cargo test`
- `lean-ctx -c npm install`
Write, StrReplace, Delete have no nebu-ctx equivalent — use them normally.