yeahno

Warning

This project is experimental. API may change.

Define a form once. Run it as a TUI, CLI, or MCP tools. For administrative bots and humans alike!

Built on huh, Cobra, and Go's official MCP SDK.

Install

go get github.com/mhpenta/yeahno

Usage

var choice string

menu := yeahno.NewSelect[string]().
    Title("Site Manager").
    ToolPrefix("site").  // Tools will be "site_add", "site_list"
    Options(
        yeahno.NewOption("Add", "add").
            Description("Register a new site for monitoring. Saves to the sites table.").
            WithField(yeahno.NewInput().Key("domain").Format("domain")).
            MCP(true),

        yeahno.NewOption("List", "list").
            Description("List all monitored sites. Returns a formatted text list.").
            MCP(true),

        yeahno.NewOption("Admin", "admin"),  // TUI only
    ).
    Value(&choice).
    Handler(func(ctx context.Context, action string, fields map[string]string) (any, error) {
        // Handle both TUI and MCP calls here
        return nil, nil
    })

// Run as TUI
result, err := menu.Run(ctx)

// Or generate CLI commands (uses Cobra + fang for styled output)
rootCmd := &cobra.Command{Use: "myapp", Short: "My app"}
menu.RegisterCLI(rootCmd)
fang.Execute(ctx, rootCmd, fang.WithColorSchemeFunc(yeahno.DefaultTheme().FangColorScheme()))

// Or register as MCP tools
menu.RegisterTools(server)

Each MCP-enabled option becomes its own tool (or CLI subcommand) with a clean schema containing only that option's fields.

API

Select Methods

Method	Description
.ToolPrefix(prefix)	Prefix for all tool names (e.g., "site" → "site_add")
.Handler(fn)	Shared handler for TUI, CLI, and MCP
.ToTools()	Generate []ToolDef (tool + handler pairs)
.RegisterTools(server)	Register all tools with MCP server
.RegisterCLI(cmd)	Register all subcommands with Cobra command
.CLI()	Generate standalone Cobra command tree

Option Methods

Method	Description
.MCP(true)	Expose option as an MCP tool
.Description(text)	Tool description
.ToolName(name)	Override default tool name
.WithField(input)	Attach input field to this option

Input Methods

Method	Description
.Key(key)	Field key in schema
.Title(text)	Field description
.Required(bool)	Mark field as required (default: true)
.Format(format)	Validation format: "domain", "uri"
.Validate(fn)	Custom validation function

Options not marked with .MCP(true) are hidden from LLMs and CLI but available in TUI.

CLI

The CLI is generated from the same menu definition. Required flags are shown inline in help output:

$ myapp --help

  COMMANDS

    add-task --title <value> [--flags]    Create a new task
    complete-task --id <value>            Mark task as done
    list-tasks                            Show all tasks

Theming

yeahno includes a default theme, or customize with your own colors:

// Use default theme
theme := yeahno.DefaultTheme()

// Or customize
theme := yeahno.DefaultTheme().
    WithPrimary(lipgloss.Color("#00ff00")).
    WithError(lipgloss.Color("#ff0000"))

// Pass to fang
fang.Execute(ctx, rootCmd, fang.WithColorSchemeFunc(theme.FangColorScheme()))

Theme Field	Usage
Primary	Titles, commands
Secondary	Flags, arguments
Muted	Descriptions, dimmed text
Surface	Code block background (light terminal)
SurfaceLight	Code block background (dark terminal)
Error	Error header

Tips for MCP Tools

Write Clear Descriptions

The .Description() text becomes the MCP tool's description that LLMs see when deciding which tool to use. Write descriptions that:

• Explain what the tool does clearly and concisely
• Specify output format (e.g., "Returns JSON data" vs "Returns Markdown text")
• Mention where data is stored if applicable (e.g., "Saved to the users table")
• Distinguish similar tools - if you have multiple tools that sound similar, make their differences explicit

// ❌ Bad: Vague, doesn't help LLM distinguish from similar tools
yeahno.NewOption("Create Job", "create_job").
    Description("Create a job")

// ✅ Good: Clear output format, storage location, and purpose
yeahno.NewOption("Create Job", "create_job").
    Description("Create a new repair job ticket. Saves to the jobs table and returns the job ID.")

Avoid fmt.Print in Handlers

Caution

Never use fmt.Print, fmt.Println, or fmt.Printf in MCP tool handlers when running in stdio mode.

MCP stdio transport uses stdout for JSON-RPC communication. Any text written to stdout (including debug prints) will corrupt the JSON stream and cause errors like:

ERROR calling "tools/call": invalid character '=' looking for beginning of value

Use slog or another logger configured to write to stderr instead:

// ❌ Bad: Corrupts MCP stdio communication
fmt.Println("Processing request...")

// ✅ Good: Logs to stderr, not stdout
slog.Info("Processing request...")

Example

menu := yeahno.NewSelect[string]().
    Title("Company").
    ToolPrefix("company").
    Options(
        yeahno.NewOption("Add & Monitor", "add_monitor").
            Description("Add a company and begin monitoring for changes. Saves to companies table.").
            WithField(yeahno.NewInput().Key("domain").Format("domain")).
            WithField(yeahno.NewInput().Key("name").Title("Company name")).
            WithField(yeahno.NewInput().Key("ticker").Required(false)).
            MCP(true),

        yeahno.NewOption("List", "list").
            Description("List all monitored companies. Returns a formatted text list.").
            MCP(true),

        yeahno.NewOption("Cancel", "cancel"),  // TUI only
    ).
    Handler(myHandler)

// Generates 2 tools:
// - company_add_monitor (with domain, name, ticker fields)
// - company_list (no fields)
tools, _ := menu.ToTools()

Supported Types

huh	yeahno
NewSelect[T]()	Yes
NewInput()	Yes
NewText()	Yes
NewConfirm()	Yes
NewMultiSelect[T]()	Yes

License

MIT