The Sley DSL

A Sley body describes a native command's syntax. Quote option spellings ('--help', '-h') so PowerShell passes them as names rather than binding them as verb parameters.

Verb	Valid scopes	Parameters	Body scope
Sley	DraftScope	Name, Alias, Description, mandatory Body	CompleterScope
Command	CompleterScope, CommandScope	Name, Alias, Description, optional Body	CommandScope
Option	CompleterScope, CommandScope, OptionGroupScope	Name, Alias, Description, optional Body	OptionScope
OptionGroup	CompleterScope	Name, mandatory Body	OptionGroupScope
Use	CompleterScope, CommandScope	Kind (OptionGroup), Name	None
Argument	CompleterScope, CommandScope, OptionScope	Name, Variadic, Source, Provider, CacheKey	None

The reference gives exact types, positions and mandatory flags for every parameter.

Invoke-Loom {
    Thread Reed
    Sley tool -Alias tool.exe -Description 'Example native tool' {
        OptionGroup common {
            Option '--verbose' -Alias '-v'
            Option '--format' { Argument format -Source { 'json'; 'text' } }
        }
        Use OptionGroup common
        Command files {
            Use OptionGroup common
            Argument path -Variadic
        }
    }
}

Command nests to any depth. An Option without a value is a switch; one with Argument takes one value. Argument at command level adds a positional slot; a variadic slot consumes the remaining positions and must come last. The declaration validator checks duplicate names/aliases and malformed trees; errors prevent registration, warnings remain visible.

OptionGroup alone contributes no candidates. Declare it before Use OptionGroup name; use copies its options immediately into the target command. There is no implicit inheritance from parent command declarations.

Outside a draft, New-Completer accepts the same body as Sley and returns a definition:

Import-Module PSLoom.Reed
$definition = New-Completer tool { Command files { Argument path -Variadic } }
$definition | Test-Completer
$definition | Register-Completer

Source scripts are ordinary scripts executed later, not DSL scope bodies. See sources, providers and cache.