diff --git a/README.md b/README.md
index f9d4d47..db6cef3 100644
--- a/README.md
+++ b/README.md
@@ -411,6 +411,54 @@ pnpm add @byjohann/toon
 yarn add @byjohann/toon
 ```
 
+## CLI
+
+Command-line tool for converting between JSON and TOON formats.
+
+### Usage
+
+```bash
+npx @byjohann/toon <input> [options]
+```
+
+**Auto-detection:** The CLI automatically detects the operation based on file extension (`.json` → encode, `.toon` → decode).
+
+```bash
+# Encode JSON to TOON (auto-detected)
+toon input.json -o output.toon
+
+# Decode TOON to JSON (auto-detected)
+toon data.toon -o output.json
+
+# Output to stdout
+toon input.json
+```
+
+### Options
+
+| Option | Description |
+| ------ | ----------- |
+| `-o, --output <file>` | Output file path (prints to stdout if omitted) |
+| `-e, --encode` | Force encode mode (overrides auto-detection) |
+| `-d, --decode` | Force decode mode (overrides auto-detection) |
+| `--delimiter <char>` | Array delimiter: `,` (comma), `\t` (tab), `\|` (pipe) |
+| `--indent <number>` | Indentation size (default: `2`) |
+| `--length-marker` | Add `#` prefix to array lengths (e.g., `items[#3]`) |
+| `--no-strict` | Disable strict validation when decoding |
+
+### Examples
+
+```bash
+# Tab-separated output (often more token-efficient)
+toon data.json --delimiter "\t" -o output.toon
+
+# Pipe-separated with length markers
+toon data.json --delimiter "|" --length-marker -o output.toon
+
+# Lenient decoding (skip validation)
+toon data.toon --no-strict -o output.json
+```
+
 ## Quick Start
 
 ```ts
diff --git a/bin/toon.mjs b/bin/toon.mjs
new file mode 100644
index 0000000..37a89e8
--- /dev/null
+++ b/bin/toon.mjs
@@ -0,0 +1,3 @@
+#!/usr/bin/env node
+'use strict'
+import('../dist/cli/index.js')
diff --git a/cli/package.json b/cli/package.json
new file mode 100644
index 0000000..04a9499
--- /dev/null
+++ b/cli/package.json
@@ -0,0 +1,12 @@
+{
+  "name": "@toon/cli",
+  "type": "module",
+  "private": true,
+  "scripts": {
+    "dev": "tsx ./src/index.ts"
+  },
+  "dependencies": {
+    "citty": "^0.1.6",
+    "consola": "^3.4.2"
+  }
+}
diff --git a/cli/src/index.ts b/cli/src/index.ts
new file mode 100644
index 0000000..b33a6f3
--- /dev/null
+++ b/cli/src/index.ts
@@ -0,0 +1,197 @@
+import type { DecodeOptions, EncodeOptions } from '../../src'
+import * as fsp from 'node:fs/promises'
+import * as path from 'node:path'
+import process from 'node:process'
+import { defineCommand, runMain } from 'citty'
+import { consola } from 'consola'
+import { version } from '../../package.json' with { type: 'json' }
+import { decode, DELIMITERS, encode } from '../../src'
+
+const main = defineCommand({
+  meta: {
+    name: 'toon',
+    description: 'TOON CLI — Convert between JSON and TOON formats',
+    version,
+  },
+  args: {
+    input: {
+      type: 'positional',
+      description: 'Input file path',
+      required: true,
+    },
+    output: {
+      type: 'string',
+      description: 'Output file path',
+      alias: 'o',
+    },
+    encode: {
+      type: 'boolean',
+      description: 'Encode JSON to TOON (auto-detected by default)',
+      alias: 'e',
+    },
+    decode: {
+      type: 'boolean',
+      description: 'Decode TOON to JSON (auto-detected by default)',
+      alias: 'd',
+    },
+    delimiter: {
+      type: 'string',
+      description: 'Delimiter for arrays: comma (,), tab (\\t), or pipe (|)',
+      default: ',',
+    },
+    indent: {
+      type: 'string',
+      description: 'Indentation size',
+      default: '2',
+    },
+    lengthMarker: {
+      type: 'boolean',
+      description: 'Use length marker (#) for arrays',
+      default: false,
+    },
+    strict: {
+      type: 'boolean',
+      description: 'Enable strict mode for decoding',
+      default: true,
+    },
+  },
+  async run({ args }) {
+    const input = args.input || args._[0]
+    if (!input) {
+      throw new Error('Input file path is required')
+    }
+
+    const inputPath = path.resolve(input)
+    const outputPath = args.output ? path.resolve(args.output) : undefined
+
+    // Parse and validate indent
+    const indent = Number.parseInt(args.indent || '2', 10)
+    if (Number.isNaN(indent) || indent < 0) {
+      throw new Error(`Invalid indent value: ${args.indent}`)
+    }
+
+    // Validate delimiter
+    const delimiter = args.delimiter || ','
+    if (!Object.values(DELIMITERS).includes(delimiter as any)) {
+      throw new Error(`Invalid delimiter "${delimiter}". Valid delimiters are: comma (,), tab (\\t), pipe (|)`)
+    }
+
+    const mode = detectMode(inputPath, args.encode, args.decode)
+
+    try {
+      if (mode === 'encode') {
+        await encodeToToon({
+          input: inputPath,
+          output: outputPath,
+          delimiter: delimiter as ',' | '\t' | '|',
+          indent,
+          lengthMarker: args.lengthMarker === true ? '#' : false,
+        })
+      }
+      else {
+        await decodeToJson({
+          input: inputPath,
+          output: outputPath,
+          indent,
+          strict: args.strict !== false,
+        })
+      }
+    }
+    catch (error) {
+      consola.error(error)
+      process.exit(1)
+    }
+  },
+})
+
+function detectMode(
+  inputFile: string,
+  encodeFlag?: boolean,
+  decodeFlag?: boolean,
+): 'encode' | 'decode' {
+  // Explicit flags take precedence
+  if (encodeFlag)
+    return 'encode'
+  if (decodeFlag)
+    return 'decode'
+
+  // Auto-detect based on file extension
+  if (inputFile.endsWith('.json'))
+    return 'encode'
+  if (inputFile.endsWith('.toon'))
+    return 'decode'
+
+  // Default to encode
+  return 'encode'
+}
+
+async function encodeToToon(config: {
+  input: string
+  output?: string
+  delimiter: ',' | '\t' | '|'
+  indent: number
+  lengthMarker: '#' | false
+}) {
+  const jsonContent = await fsp.readFile(config.input, 'utf-8')
+
+  let data: unknown
+  try {
+    data = JSON.parse(jsonContent)
+  }
+  catch (error) {
+    throw new Error(`Failed to parse JSON: ${error instanceof Error ? error.message : String(error)}`)
+  }
+
+  const encodeOptions: EncodeOptions = {
+    delimiter: config.delimiter,
+    indent: config.indent,
+    lengthMarker: config.lengthMarker,
+  }
+
+  const toonOutput = encode(data, encodeOptions)
+
+  if (config.output) {
+    await fsp.writeFile(config.output, toonOutput, 'utf-8')
+    const relativeInputPath = path.relative(process.cwd(), config.input)
+    const relativeOutputPath = path.relative(process.cwd(), config.output)
+    consola.success(`Encoded \`${relativeInputPath}\` → \`${relativeOutputPath}\``)
+  }
+  else {
+    console.log(toonOutput)
+  }
+}
+
+async function decodeToJson(config: {
+  input: string
+  output?: string
+  indent: number
+  strict: boolean
+}) {
+  const toonContent = await fsp.readFile(config.input, 'utf-8')
+
+  let data: unknown
+  try {
+    const decodeOptions: DecodeOptions = {
+      indent: config.indent,
+      strict: config.strict,
+    }
+    data = decode(toonContent, decodeOptions)
+  }
+  catch (error) {
+    throw new Error(`Failed to decode TOON: ${error instanceof Error ? error.message : String(error)}`)
+  }
+
+  const jsonOutput = JSON.stringify(data, undefined, config.indent)
+
+  if (config.output) {
+    await fsp.writeFile(config.output, jsonOutput, 'utf-8')
+    const relativeInputPath = path.relative(process.cwd(), config.input)
+    const relativeOutputPath = path.relative(process.cwd(), config.output)
+    consola.success(`Decoded \`${relativeInputPath}\` → \`${relativeOutputPath}\``)
+  }
+  else {
+    console.log(jsonOutput)
+  }
+}
+
+runMain(main)
diff --git a/package.json b/package.json
index 1ec1639..7e09a54 100644
--- a/package.json
+++ b/package.json
@@ -23,6 +23,7 @@
   },
   "types": "./dist/index.d.ts",
   "files": [
+    "bin",
     "dist"
   ],
   "scripts": {
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 520ab31..23e8a37 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -93,6 +93,15 @@ importers:
         specifier: ^2.8.1
         version: 2.8.1
 
+  cli:
+    dependencies:
+      citty:
+        specifier: ^0.1.6
+        version: 0.1.6
+      consola:
+        specifier: ^3.4.2
+        version: 3.4.2
+
 packages:
 
   '@ai-sdk/anthropic@2.0.37':
diff --git a/pnpm-workspace.yaml b/pnpm-workspace.yaml
index 76137e2..4a20a92 100644
--- a/pnpm-workspace.yaml
+++ b/pnpm-workspace.yaml
@@ -1,2 +1,3 @@
 packages:
   - benchmarks
+  - cli
diff --git a/tsdown.config.ts b/tsdown.config.ts
index 0dfb197..f661973 100644
--- a/tsdown.config.ts
+++ b/tsdown.config.ts
@@ -2,7 +2,10 @@ import type { UserConfig, UserConfigFn } from 'tsdown/config'
 import { defineConfig } from 'tsdown/config'
 
 const config: UserConfig | UserConfigFn = defineConfig({
-  entry: ['src/index.ts'],
+  entry: {
+    'index': 'src/index.ts',
+    'cli/index': 'cli/src/index.ts',
+  },
   dts: true,
 })