Kong (Go CLI parser)
Sophisticated CLI parser for Go using struct tags to define commands, flags, and arguments. Kong uses Go struct definitions as the single source of truth for CLI interface — annotate structs with tags like `cmd:""`, `flag:""`, `arg:""`, `help:""`. Supports subcommands, aliases, environment variable binding, and custom type decoders. A more powerful alternative to cobra for teams wanting type-safe, struct-driven CLI definition.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
CLI parsing library. No external calls. Input validation from struct tags helps prevent invalid config.
⚡ Reliability
Best When
You're building a new Go CLI tool and want struct-driven command definition with type safety — kong's approach reduces boilerplate vs cobra's builder pattern.
Avoid When
You have an existing cobra CLI or need cobra's extensive plugin and completion tooling ecosystem.
Use Cases
- • Build Go CLI tools with complex subcommand hierarchies defined as struct types with kong tags for type safety
- • Create agent CLI tools in Go where each subcommand is a typed struct with automatic help generation and validation
- • Define CLI flags that bind to environment variables automatically without manual os.Getenv() code
- • Build configuration-driven CLIs where command structs are populated from both CLI args and environment in one pass
- • Replace cobra in Go projects that prefer struct-tag-driven CLI definition over builder-pattern command registration
Not For
- • Teams with existing cobra codebase — migration cost is high; kong's approach is fundamentally different
- • Very simple CLIs with 1-2 flags — standard flag package or pflag may be simpler
- • Projects requiring cobra's plugin ecosystem (cobra-gen, completion framework) — cobra has more tooling
Interface
Authentication
CLI parsing library. No authentication required.
Pricing
MIT license.
Agent Metadata
Known Gotchas
- ⚠ Kong requires exactly one kong.Parse(&cli) call which sets up the entire CLI from struct tags — the CLI struct must be fully defined before parsing
- ⚠ Subcommand Run() methods must be defined on each command struct — Kong calls Run() on the matched subcommand; missing Run causes a build-time error
- ⚠ Struct embedding for shared flags is supported but requires careful tag design — embedded struct fields appear at the parent level unless explicitly named
- ⚠ Environment variable binding uses the `env:"VAR_NAME"` tag — env vars are lower priority than CLI flags; order of precedence: flag > env > default
- ⚠ Custom types require implementing the kong.Decoder interface — built-in support for time.Duration, url.URL, and slice types; others need custom decoders
- ⚠ Help text uses the struct field tag `help:""` — field names without help tags show the field name in help output which may not be user-friendly
Alternatives
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Scores are editorial opinions as of 2026-03-07.