diff --git a/README.md b/README.md
index 20ddaa4..4091662 100644
--- a/README.md
+++ b/README.md
@@ -44,7 +44,7 @@ bun run compile
 
 Requires [Bun](https://bun.sh) >= 1.2 and [Zig](https://ziglang.org/) (OpenTUI native bindings).
 
-## Configuration
+## Quick start
 
 Config and cookies are stored under `~/.codimd/` by default.
 
@@ -56,33 +56,280 @@ codimd-cli whoami
 codimd-cli list
 ```
 
+You can also pass the server per invocation:
+
+```bash
+codimd-cli -s https://your-codimd.example.com list
+```
+
+Run `codimd-cli --help` or `codimd-cli <command> --help` for the full usage text.
+
+## Configuration
+
+Settings are merged from `~/.codimd/config.json`, environment variables, and CLI flags (highest priority).
+
 | Variable | Description |
 |----------|-------------|
 | `CMD_CLI_SERVER_URL` | CodiMD server URL |
 | `CMD_CLI_CONFIG_DIR` | Config directory (default `~/.codimd`) |
-| `CMD_CLI_COOKIE_PATH` | Cookie file path |
-| `CMD_CLI_ID` / `CMD_CLI_PASSWORD` | Non-interactive login |
-
-## Commands
-
-| Command | Description |
-|---------|-------------|
-| `login` | Sign in with email/password or `--ldap` |
-| `logout` | Clear session |
-| `whoami` | Current user info (`GET /me`) |
-| `config set/show` | Manage local config |
-| `list` | List owned notes (`GET /api/notes/myNotes`) |
-| `show <noteId>` | Print note markdown (`GET /:id/download`) |
-| `info <noteId>` | Note metadata JSON (`GET /:id/info`) |
-| `create [file]` | Create note from file or stdin (`POST /new`) |
-| `import [file]` | Alias of `create` |
-| `update <noteId> [file]` | Update note content (`PUT /api/notes/:id`) |
-| `delete <noteId>` | Delete owned note (`DELETE /api/notes/:id`) |
-| `export <noteId> [file]` | Export note (`--md`, `--html`, `--pdf`) |
-| `history` | Browsing history (`GET /history`, `--pin` / `--unpin`) |
-| `open <noteId>` | Open note URL in the default browser |
-| `tui` | Interactive note browser (OpenTUI) |
-| *(stdin pipe)* | `cat doc.md \| codimd-cli` creates a note |
+| `CMD_CLI_COOKIE_PATH` | Cookie file path (default `~/.codimd/cookies.json`) |
+| `CMD_CLI_ID` | Email or username for non-interactive login |
+| `CMD_CLI_PASSWORD` | Password for non-interactive login |
+
+### Global options
+
+Available on every command:
+
+| Option | Description |
+|--------|-------------|
+| `-s, --server <url>` | Override the configured CodiMD server URL |
+| `-h, --help` | Show help (short descriptions with `-h`, full with `--help`) |
+| `-V, --version` | Print version |
+
+## Command reference
+
+### Authentication
+
+#### `login`
+
+Sign in with email/password or LDAP. Prompts interactively when credentials are not provided.
+
+```bash
+codimd-cli login
+codimd-cli login -u you@example.com
+codimd-cli login --ldap -u ldap-user
+```
+
+| Option | Description |
+|--------|-------------|
+| `-u, --id <id>` | Email or username |
+| `--ldap` | Use LDAP authentication (`POST /auth/ldap`) |
+
+Credentials can also come from `CMD_CLI_ID` / `CMD_CLI_PASSWORD` or saved config.
+
+#### `logout`
+
+Clear the session cookie and call the server logout endpoint.
+
+```bash
+codimd-cli logout
+```
+
+#### `whoami`
+
+Print the current user as JSON (`GET /me`).
+
+```bash
+codimd-cli whoami
+```
+
+### Configuration
+
+#### `config set <key> <value>`
+
+Persist a config value to `~/.codimd/config.json`.
+
+```bash
+codimd-cli config set serverUrl https://your-codimd.example.com
+```
+
+Supported keys: `serverUrl`.
+
+#### `config show`
+
+Print the effective merged configuration as JSON.
+
+```bash
+codimd-cli config show
+```
+
+### Notes
+
+Note IDs are the short alphanumeric strings from CodiMD URLs (for example `abc123` from `https://your-codimd.example.com/abc123`).
+
+#### `list`
+
+List notes you own (`GET /api/notes/myNotes`).
+
+```bash
+codimd-cli list
+codimd-cli list --json
+```
+
+| Option | Description |
+|--------|-------------|
+| `--json` | Output raw JSON instead of a table |
+
+#### `show <noteId>`
+
+Print note markdown to stdout (`GET /:noteId/download`).
+
+```bash
+codimd-cli show abc123
+codimd-cli show abc123 > note.md
+```
+
+#### `info <noteId>`
+
+Print note metadata as JSON (`GET /:noteId/info`).
+
+```bash
+codimd-cli info abc123
+```
+
+#### `create [file]` / `import [file]`
+
+Create a note from a file or stdin (`POST /new`). `import` is an alias of `create`.
+
+```bash
+codimd-cli create draft.md
+echo "# Hello" | codimd-cli create
+cat draft.md | codimd-cli import
+```
+
+On success, prints the new note URL to stdout.
+
+#### `update <noteId> [file]`
+
+Replace note content from a file or stdin (`PUT /api/notes/:noteId`).
+
+```bash
+codimd-cli update abc123 revised.md
+cat revised.md | codimd-cli update abc123
+```
+
+#### `delete <noteId>`
+
+Delete a note you own (`DELETE /api/notes/:noteId`). Prompts for confirmation unless `--yes` is passed.
+
+```bash
+codimd-cli delete abc123
+codimd-cli delete abc123 --yes
+```
+
+| Option | Description |
+|--------|-------------|
+| `-y, --yes` | Skip confirmation prompt |
+
+#### `export <noteId> [output]`
+
+Export a note to stdout or a file.
+
+```bash
+codimd-cli export abc123                    # markdown to stdout
+codimd-cli export abc123 --html             # HTML to stdout
+codimd-cli export abc123 --pdf out.pdf      # PDF to file
+codimd-cli export abc123 --md backup.md     # markdown to file
+```
+
+| Option | Description |
+|--------|-------------|
+| `--md` | Export as Markdown (default) |
+| `--html` | Export as HTML |
+| `--pdf` | Export as PDF |
+
+When no output path is given, text formats go to stdout; PDF is written as binary to stdout.
+
+#### `open <noteId>`
+
+Open the note URL in your default browser and print the URL.
+
+```bash
+codimd-cli open abc123
+```
+
+### History
+
+#### `history`
+
+Show browsing history (`GET /history`), or pin/unpin entries.
+
+```bash
+codimd-cli history
+codimd-cli history --json
+codimd-cli history --pin abc123
+codimd-cli history --unpin abc123
+```
+
+| Option | Description |
+|--------|-------------|
+| `--json` | Output raw JSON |
+| `--pin <noteId>` | Pin a history entry |
+| `--unpin <noteId>` | Unpin a history entry |
+
+### Interactive
+
+#### `tui`
+
+Launch the OpenTUI note browser. See [Interactive TUI](#interactive-tui) for keyboard shortcuts.
+
+```bash
+codimd-cli tui
+```
+
+### Stdin shortcut
+
+When no subcommand is given and stdin is not a TTY, `codimd-cli` reads stdin and creates a note (same as `create`):
+
+```bash
+cat doc.md | codimd-cli
+pbpaste | codimd-cli -s https://your-codimd.example.com
+```
+
+Prints the new note URL to stdout.
+
+## Shell completions
+
+Tab completion for commands and flags is built in via Cliffy's `CompletionsCommand`. No extra packages are required beyond the existing `@cliffy/command` dependency.
+
+Generate and enable completions for your shell:
+
+### Bash
+
+Add to `~/.bashrc`:
+
+```bash
+source <(codimd-cli completions bash)
+```
+
+### Zsh
+
+Add to `~/.zshrc`:
+
+```bash
+source <(codimd-cli completions zsh)
+```
+
+If you use Oh My Zsh, you can instead save the script once:
+
+```bash
+codimd-cli completions zsh > "${ZSH_CUSTOM:-$HOME/.oh-my-zsh/custom}/_codimd-cli"
+```
+
+### Fish
+
+Either load in the current session:
+
+```fish
+codimd-cli completions fish | source
+```
+
+Or install persistently:
+
+```fish
+mkdir -p ~/.config/fish/completions
+codimd-cli completions fish > ~/.config/fish/completions/codimd-cli.fish
+```
+
+Restart your shell or `source` the updated config file. Completions cover subcommands (`list`, `show`, …) and global flags such as `--server`.
+
+To inspect the generated script without enabling it:
+
+```bash
+codimd-cli completions bash
+codimd-cli completions zsh
+codimd-cli completions fish
+```
 
 ## CodiMD API mapping
 
diff --git a/src/cli.ts b/src/cli.ts
index c059da9..76bff0a 100644
--- a/src/cli.ts
+++ b/src/cli.ts
@@ -1,6 +1,7 @@
 #!/usr/bin/env bun
 
 import { Command } from "@cliffy/command";
+import { CompletionsCommand } from "@cliffy/command/completions";
 import pkg from "../package.json" with { type: "json" };
 
 import { config } from "./config";
@@ -63,7 +64,8 @@ const cli = new Command()
   .command("history", historyCommand)
   .command("tui", tuiCommand)
   .command("delete", deleteNoteCommand)
-  .command("open", openCommand);
+  .command("open", openCommand)
+  .command("completions", new CompletionsCommand());
 
 if (import.meta.main) {
   await cli.parse(getCliArgs());