diff --git a/README.md b/README.md
index f999f46..48774e0 100644
--- a/README.md
+++ b/README.md
@@ -28,20 +28,20 @@ dependencies {
 ## Usage
 
 ```kotlin
-fun main(args: Array<String>) = cli("application") {
+fun main(args: Array<String>) = command("application") {
     execute {
         // define execution of command (e.g., display help)
         help()
     }
 
-    // declare command "greet"
-    command("greet") {
-        // declare arguments
-        val speakersArg by argument.string("speakers").variable(min = 1)
+    // register command "greet"
+    +command("greet") {
+        // declare and register arguments
+        val speakersArg = +argument.string("speakers").variable(min = 1)
 
-        // declare options
-        val greetingOpt by option.string("greeting", "greet", "g").orElse("Hello")
-        val nameOpt by option.string("name", "n").orNull()
+        // declare and register options
+        val greetingOpt = +option.string("greeting", "greet", "g").orElse("Hello")
+        val nameOpt = +option.string("name", "n").orNull()
 
         execute {
             // retrieve the arguments and options
@@ -52,11 +52,11 @@ fun main(args: Array<String>) = cli("application") {
             println("${speakers.joinToString()}: $greeting ${name ?: "World"}!")
         }
 
-        // declare more commands...
+        // register more commands...
     }
 
-    // declare fallback command
-    fallback.string("value") { valueArg ->
+    // register fallback command "value"
+    +command.fallback.string("value") { valueArg ->
         execute {
             // retrieve the value used for the fallback command
             val value by valueArg
diff --git a/src/commonMain/kotlin/com/infendro/cli/command/Command.kt b/src/commonMain/kotlin/com/infendro/cli/command/Command.kt
index 1690d9f..d10601f 100644
--- a/src/commonMain/kotlin/com/infendro/cli/command/Command.kt
+++ b/src/commonMain/kotlin/com/infendro/cli/command/Command.kt
@@ -8,12 +8,10 @@ import com.infendro.cli.command.help.DefaultHelpRenderer
 import com.infendro.cli.command.help.HelpRenderer
 import com.infendro.cli.command.option.Option
 import com.infendro.cli.error.build.*
-import com.infendro.cli.parser.*
+import com.infendro.cli.parser.Parser
 import com.infendro.cli.util.Regex
-import kotlin.reflect.KProperty
 
 sealed class Command private constructor(
-    val parent: Command?,
     val name: String,
     val commands: List<Command>,
     val arguments: List<Argument<*>>,
@@ -21,22 +19,21 @@ sealed class Command private constructor(
     internal val execute: Context.() -> Unit,
     internal val renderer: HelpRenderer,
 ) {
-    val path: List<Command>
-        get() = when {
-            parent == null -> listOf(this)
-            else -> parent.path + this
-        }
-
-    val help: String?
-        get() = renderer.render(this)
+    init {
+        if (!name.matches(Regex.COMMAND)) throw InvalidCommand(name)
+    }
 
     fun run(args: Array<String>) {
         when (val result = ContextParser(this, args).parse()) {
             is ContextParser.Result.Success -> result.context.execute()
-            is ContextParser.Result.Help -> result.command.help?.let { print(it) }
+            is ContextParser.Result.Help -> {
+                val command = result.path.last()
+                command.renderer.render(result.path)?.let { print(it) }
+            }
             is ContextParser.Result.Failure -> {
                 println("error: ${result.error.message}")
-                result.command.help?.let {
+                val command = result.path.last()
+                command.renderer.render(result.path)?.let {
                     println()
                     print(it)
                 }
@@ -45,24 +42,22 @@ sealed class Command private constructor(
     }
 
     class Named(
-        parent: Command?,
         name: String,
         commands: List<Command>,
         arguments: List<Argument<*>>,
         options: List<Option<*>>,
         execute: Context.() -> Unit,
         renderer: HelpRenderer,
-    ) : Command(parent, name, commands, arguments, options, execute, renderer) {
+    ) : Command(name, commands, arguments, options, execute, renderer) {
         class Builder(
             name: String,
         ) : Command.Builder<Named>(name) {
             override fun create() =
-                Named(parent, name, commands, arguments, options, execute, renderer)
+                Named(name, commands, arguments, options, execute, renderer)
         }
     }
 
     class Fallback<T : Any>(
-        parent: Command?,
         val key: Key<T>,
         val parser: Parser<T>,
         name: String,
@@ -71,7 +66,7 @@ sealed class Command private constructor(
         options: List<Option<*>>,
         execute: Context.() -> Unit,
         renderer: HelpRenderer,
-    ) : Command(parent, name, commands, arguments, options, execute, renderer) {
+    ) : Command(name, commands, arguments, options, execute, renderer) {
         class Builder<T : Any>(
             val parser: Parser<T>,
             name: String,
@@ -79,7 +74,7 @@ sealed class Command private constructor(
             internal val key = Key<T>()
 
             override fun create() =
-                Fallback(parent, key, parser, name, commands, arguments, options, execute, renderer)
+                Fallback(key, parser, name, commands, arguments, options, execute, renderer)
         }
 
         class Key<T>
@@ -89,8 +84,6 @@ sealed class Command private constructor(
     sealed class Builder<COMMAND : Command>(
         protected val name: String,
     ) {
-        protected var parent: Command? = null
-        private val builders = mutableListOf<Builder<*>>()
         protected val commands = mutableListOf<Command>()
         protected val arguments = mutableListOf<Argument<*>>()
         protected val options = mutableListOf<Option<*>>()
@@ -102,40 +95,13 @@ sealed class Command private constructor(
         protected val renderer: HelpRenderer
             get() = _renderer!!
 
-        fun command(name: String, block: Builder<*>.() -> Unit) {
-            validateCommand(name)
-            builders += Named.Builder(name).apply(block)
+        fun register(command: Command) {
+            validateCommand(command)
+            commands += command
         }
 
-        inner class FallbackFactory {
-            fun string(name: String, block: Builder<*>.(Fallback.Key<String>) -> Unit) =
-                fallback(StringParser, name, block)
-
-            fun int(name: String, block: Builder<*>.(Fallback.Key<Int>) -> Unit) =
-                fallback(IntParser, name, block)
-
-            fun long(name: String, block: Builder<*>.(Fallback.Key<Long>) -> Unit) =
-                fallback(LongParser, name, block)
-
-            fun float(name: String, block: Builder<*>.(Fallback.Key<Float>) -> Unit) =
-                fallback(FloatParser, name, block)
-
-            fun double(name: String, block: Builder<*>.(Fallback.Key<Double>) -> Unit) =
-                fallback(DoubleParser, name, block)
-
-            fun boolean(name: String, block: Builder<*>.(Fallback.Key<Boolean>) -> Unit) =
-                fallback(BooleanParser, name, block)
-
-            inline fun <reified T : Enum<T>> enum(name: String, noinline block: Builder<*>.(Fallback.Key<T>) -> Unit) =
-                fallback(enumParser<T>(), name, block)
-        }
-
-        val fallback = FallbackFactory()
-
-        fun <T : Any> fallback(parser: Parser<T>, name: String, block: Fallback.Builder<T>.(Fallback.Key<T>) -> Unit) {
-            validateCommand(name)
-            builders += Fallback.Builder(parser, name).apply { block(key) }
-        }
+        fun register(vararg commands: Command) = commands.forEach(::register)
+        operator fun <T : Command> T.unaryPlus() = also(::register)
 
         fun register(argument: Argument<*>) {
             validateArgument(argument)
@@ -143,9 +109,7 @@ sealed class Command private constructor(
         }
 
         fun register(vararg arguments: Argument<*>) = arguments.forEach(::register)
-
-        operator fun <T : Argument<*>> T.provideDelegate(thisRef: Nothing?, property: KProperty<*>) = also(::register)
-        operator fun <T : Argument<*>> T.getValue(thisRef: Nothing?, property: KProperty<*>) = this
+        operator fun <T : Argument<*>> T.unaryPlus() = also(::register)
 
         fun register(option: Option<*>) {
             validateOption(option)
@@ -153,9 +117,7 @@ sealed class Command private constructor(
         }
 
         fun register(vararg options: Option<*>) = options.forEach(::register)
-
-        operator fun <T : Option<*>> T.provideDelegate(thisRef: Nothing?, property: KProperty<*>) = also(::register)
-        operator fun <T : Option<*>> T.getValue(thisRef: Nothing?, property: KProperty<*>) = this
+        operator fun <T : Option<*>> T.unaryPlus() = also(::register)
 
         fun execute(block: Context.() -> Unit) {
             validateExecute()
@@ -167,32 +129,22 @@ sealed class Command private constructor(
             _renderer = renderer
         }
 
+        internal abstract fun create(): COMMAND
+
         internal fun build(): Command {
             if (_execute == null) _execute = {}
             if (_renderer == null) _renderer = DefaultHelpRenderer
 
             validate()
-            val command = create()
-
-            for (builder in builders) {
-                builder.parent = command
-                commands += builder.build()
-            }
-
-            return command
+            return create()
         }
 
-        internal abstract fun create(): COMMAND
-
-        private fun validateCommand(name: String) {
-            if (builders.isNotEmpty()) {
-                val last = builders.last()
-                if (last is Fallback.Builder<*>) throw InvalidCommandOrder()
-            }
-            when {
-                !name.matches(Regex.COMMAND) -> throw InvalidCommand(name)
-                builders.any { it.name == name } -> throw DuplicateCommand(name)
+        private fun validateCommand(command: Command) {
+            if (commands.isNotEmpty()) {
+                val last = commands.last()
+                if (last is Fallback<*>) throw InvalidCommandOrder()
             }
+            if (commands.any { it.name == command.name }) throw DuplicateCommand(command.name)
         }
 
         private fun validateArgument(argument: Argument<*>) {
@@ -203,6 +155,7 @@ sealed class Command private constructor(
                     argument.required && last.optional -> throw InvalidArgumentOrder()
                 }
             }
+            if (arguments.any { it.name == argument.name }) throw DuplicateArgument(argument.name)
         }
 
         private fun validateOption(option: Option<*>) {
@@ -220,10 +173,7 @@ sealed class Command private constructor(
         }
 
         private fun validate() {
-            if (builders.any { it is Fallback.Builder<*> } && arguments.isNotEmpty()) throw InvalidFallback()
+            if (commands.any { it is Fallback<*> } && arguments.isNotEmpty()) throw InvalidFallback()
         }
     }
 }
-
-fun cli(name: String, block: Command.Builder<*>.() -> Unit) =
-    Command.Named.Builder(name).apply(block).build()
diff --git a/src/commonMain/kotlin/com/infendro/cli/command/CommandFactory.kt b/src/commonMain/kotlin/com/infendro/cli/command/CommandFactory.kt
new file mode 100644
index 0000000..bef9ef8
--- /dev/null
+++ b/src/commonMain/kotlin/com/infendro/cli/command/CommandFactory.kt
@@ -0,0 +1,39 @@
+package com.infendro.cli.command
+
+import com.infendro.cli.command.Command.*
+import com.infendro.cli.parser.*
+
+class CommandFactory internal constructor() {
+    inner class FallbackFactory internal constructor() {
+        fun string(name: String, block: Builder<*>.(Fallback.Key<String>) -> Unit) =
+            fallback(StringParser, name, block)
+
+        fun int(name: String, block: Builder<*>.(Fallback.Key<Int>) -> Unit) =
+            fallback(IntParser, name, block)
+
+        fun long(name: String, block: Builder<*>.(Fallback.Key<Long>) -> Unit) =
+            fallback(LongParser, name, block)
+
+        fun float(name: String, block: Builder<*>.(Fallback.Key<Float>) -> Unit) =
+            fallback(FloatParser, name, block)
+
+        fun double(name: String, block: Builder<*>.(Fallback.Key<Double>) -> Unit) =
+            fallback(DoubleParser, name, block)
+
+        fun boolean(name: String, block: Builder<*>.(Fallback.Key<Boolean>) -> Unit) =
+            fallback(BooleanParser, name, block)
+
+        inline fun <reified T : Enum<T>> enum(name: String, noinline block: Builder<*>.(Fallback.Key<T>) -> Unit) =
+            fallback(enumParser<T>(), name, block)
+    }
+
+    fun <T : Any> fallback(parser: Parser<T>, name: String, block: Fallback.Builder<T>.(Fallback.Key<T>) -> Unit) =
+        Fallback.Builder(parser, name).apply { block(key) }.build()
+
+    val fallback = FallbackFactory()
+}
+
+fun command(name: String, block: Builder<*>.() -> Unit) =
+    Named.Builder(name).apply(block).build()
+
+val command = CommandFactory()
diff --git a/src/commonMain/kotlin/com/infendro/cli/command/context/Context.kt b/src/commonMain/kotlin/com/infendro/cli/command/context/Context.kt
index 5084cb0..9f1c866 100644
--- a/src/commonMain/kotlin/com/infendro/cli/command/context/Context.kt
+++ b/src/commonMain/kotlin/com/infendro/cli/command/context/Context.kt
@@ -8,15 +8,18 @@ import kotlin.reflect.KProperty
 
 @Dsl
 class Context internal constructor(
-    val command: Command,
+    private val path: List<Command>,
     private val commands: Map<Command.Fallback.Key<*>, Any>,
     private val arguments: Map<Argument<*>, List<Any>>,
     private val options: Map<Option<*>, List<Any>>,
 ) {
+    val command: Command
+        get() = path.last()
+
     internal fun execute() = (command.execute)()
 
     fun help() {
-        command.help?.let { print(it) }
+        command.renderer.render(path)?.let { print(it) }
     }
 
     @Suppress("UNCHECKED_CAST")
diff --git a/src/commonMain/kotlin/com/infendro/cli/command/context/ContextParser.kt b/src/commonMain/kotlin/com/infendro/cli/command/context/ContextParser.kt
index 4caf619..04d4e5c 100644
--- a/src/commonMain/kotlin/com/infendro/cli/command/context/ContextParser.kt
+++ b/src/commonMain/kotlin/com/infendro/cli/command/context/ContextParser.kt
@@ -14,18 +14,18 @@ internal class ContextParser(
         ) : Result()
 
         data class Help(
-            val command: Command,
+            val path: List<Command>,
         ) : Result()
 
         data class Failure(
-            val command: Command,
+            val path: List<Command>,
             val error: RunError,
         ) : Result()
     }
 
     private fun success(context: Context) = Result.Success(context)
-    private fun help(command: Command) = Result.Help(command)
-    private fun failure(command: Command, exception: RunError) = Result.Failure(command, exception)
+    private fun help(path: List<Command>) = Result.Help(path)
+    private fun failure(path: List<Command>, exception: RunError) = Result.Failure(path, exception)
 
     private var index = 0
     private val current: String
@@ -41,6 +41,7 @@ internal class ContextParser(
     fun parse(): Result {
         // command
         var command = root
+        val path = mutableListOf(root)
         val commands = mutableMapOf<Command.Fallback.Key<*>, Any>()
 
         while (hasNext()) {
@@ -52,16 +53,17 @@ internal class ContextParser(
             }
             if (cmd == null) {
                 when {
-                    command.arguments.isEmpty() -> return failure(command, UnknownCommand(current))
+                    command.arguments.isEmpty() -> return failure(path, UnknownCommand(current))
                     else -> break
                 }
             }
 
             command = cmd
+            path += cmd
             if (cmd is Command.Fallback<*>) {
                 val value = when (val result = cmd.parser.parse(current)) {
                     is Parser.Result.Success<*> -> result.value
-                    is Parser.Result.Failure<*> -> return failure(command, result.error)
+                    is Parser.Result.Failure<*> -> return failure(path, result.error)
                 }
                 commands[cmd.key] = value
             }
@@ -85,11 +87,11 @@ internal class ContextParser(
                 // argument
                 endOfOptions || dashes == 0 -> {
                     val argument = command.arguments.getOrNull(argumentIndex)
-                        ?: return failure(command, UnexpectedArgument())
+                        ?: return failure(path, UnexpectedArgument())
 
                     val value = when (val result = argument.parser.parse(trimmed)) {
                         is Parser.Result.Success<*> -> result.value
-                        is Parser.Result.Failure<*> -> return failure(command, result.error)
+                        is Parser.Result.Failure<*> -> return failure(path, result.error)
                     }
                     arguments[argument]!! += value
                     argumentCount++
@@ -109,7 +111,7 @@ internal class ContextParser(
                     }
 
                     if (dashes == 2 && trimmed == "help")
-                        return help(command)
+                        return help(path)
 
                     val (name, text) = when {
                         trimmed.contains('=') -> {
@@ -133,16 +135,16 @@ internal class ContextParser(
 
                     for (name in names) {
                         val option = command.options.firstOrNull { name in it.names }
-                            ?: return failure(command, UnknownOption(name))
+                            ?: return failure(path, UnknownOption(name))
 
                         val value = when {
                             text != null ->
                                 when (val result = option.parser.parse(current)) {
                                     is Parser.Result.Success<*> -> result.value
-                                    is Parser.Result.Failure<*> -> return failure(command, result.error)
+                                    is Parser.Result.Failure<*> -> return failure(path, result.error)
                                 }
                             option.flag -> option.fallback!!
-                            else -> return failure(command, MissingOptionValue(option))
+                            else -> return failure(path, MissingOptionValue(option))
                         }
                         options[option]!! += value
                     }
@@ -153,9 +155,9 @@ internal class ContextParser(
                     when {
                         current.contains('=') -> {
                             val (option) = current.split('=', limit = 2)
-                            return failure(command, MalformedOption(option))
+                            return failure(path, MalformedOption(option))
                         }
-                        else -> return failure(command, MalformedOption(current))
+                        else -> return failure(path, MalformedOption(current))
                     }
                 }
             }
@@ -166,16 +168,16 @@ internal class ContextParser(
         // validate arguments
         for (argument in command.arguments) {
             val count = arguments[argument]!!.count()
-            if (count !in argument.min..argument.count) return failure(command, InvalidArgumentCount(argument, count))
+            if (count !in argument.min..argument.count) return failure(path, InvalidArgumentCount(argument, count))
         }
 
         // validate options
         for (option in command.options) {
             val count = options[option]!!.count()
-            if (count !in option.min..option.count) return failure(command, InvalidOptionCount(option, count))
+            if (count !in option.min..option.count) return failure(path, InvalidOptionCount(option, count))
         }
 
-        val context = Context(command, commands, arguments, options)
+        val context = Context(path, commands, arguments, options)
         return success(context)
     }
 }
diff --git a/src/commonMain/kotlin/com/infendro/cli/command/help/DefaultHelpRenderer.kt b/src/commonMain/kotlin/com/infendro/cli/command/help/DefaultHelpRenderer.kt
index 76e4b5b..50a105a 100644
--- a/src/commonMain/kotlin/com/infendro/cli/command/help/DefaultHelpRenderer.kt
+++ b/src/commonMain/kotlin/com/infendro/cli/command/help/DefaultHelpRenderer.kt
@@ -5,8 +5,10 @@ import com.infendro.cli.command.argument.Argument
 import com.infendro.cli.command.option.Option
 
 object DefaultHelpRenderer : HelpRenderer {
-    override fun render(command: Command) = buildString {
-        usage(command)
+    override fun render(path: List<Command>) = buildString {
+        val command = path.last()
+
+        usage(path)
         if (command.commands.isNotEmpty()) {
             appendLine()
             commands(command.commands)
@@ -21,9 +23,11 @@ object DefaultHelpRenderer : HelpRenderer {
         }
     }
 
-    private fun StringBuilder.usage(command: Command) {
+    private fun StringBuilder.usage(path: List<Command>) {
+        val command = path.last()
+
         append("Usage:")
-        for (command in command.path) {
+        for (command in path) {
             append(" ")
             when {
                 command is Command.Fallback<*> -> append("<${command.name}>")
diff --git a/src/commonMain/kotlin/com/infendro/cli/command/help/HelpRenderer.kt b/src/commonMain/kotlin/com/infendro/cli/command/help/HelpRenderer.kt
index 62a701c..d923c5b 100644
--- a/src/commonMain/kotlin/com/infendro/cli/command/help/HelpRenderer.kt
+++ b/src/commonMain/kotlin/com/infendro/cli/command/help/HelpRenderer.kt
@@ -3,5 +3,5 @@ package com.infendro.cli.command.help
 import com.infendro.cli.command.Command
 
 interface HelpRenderer {
-    fun render(command: Command): String?
+    fun render(path: List<Command>): String?
 }
diff --git a/src/commonMain/kotlin/com/infendro/cli/command/help/NoopHelpRenderer.kt b/src/commonMain/kotlin/com/infendro/cli/command/help/NoopHelpRenderer.kt
index f92b64e..5e6c09b 100644
--- a/src/commonMain/kotlin/com/infendro/cli/command/help/NoopHelpRenderer.kt
+++ b/src/commonMain/kotlin/com/infendro/cli/command/help/NoopHelpRenderer.kt
@@ -3,5 +3,5 @@ package com.infendro.cli.command.help
 import com.infendro.cli.command.Command
 
 object NoopHelpRenderer : HelpRenderer {
-    override fun render(command: Command) = null
+    override fun render(path: List<Command>) = null
 }
diff --git a/src/commonMain/kotlin/com/infendro/cli/error/build/DuplicateArgument.kt b/src/commonMain/kotlin/com/infendro/cli/error/build/DuplicateArgument.kt
new file mode 100644
index 0000000..fe21142
--- /dev/null
+++ b/src/commonMain/kotlin/com/infendro/cli/error/build/DuplicateArgument.kt
@@ -0,0 +1,8 @@
+package com.infendro.cli.error.build
+
+class DuplicateArgument(
+    val name: String,
+) : BuildException() {
+    override val message: String
+        get() = """duplicate argument "$name""""
+}