04-tools-prompts-user-config-and-localization.md

layout	default
title	Chapter 4: Tools, Prompts, User Config, and Localization
nav_order	4
parent	MCPB Tutorial

Chapter 4: Tools, Prompts, User Config, and Localization

Welcome to Chapter 4: Tools, Prompts, User Config, and Localization. In this part of MCPB Tutorial: Packaging and Distributing Local MCP Servers as Bundles, you will build an intuitive mental model first, then move into concrete implementation details and practical production tradeoffs.

This chapter covers how bundles declare capability surfaces and user-facing configuration.

Learning Goals

• declare static tools/prompts and generated capability flags safely
• design user_config schemas with validation and sensitive field handling
• apply localization resources for user-facing metadata
• keep host UX predictable across locales and environments

Configuration Guardrails

1. define user config with explicit type and validation constraints
2. mark sensitive fields (api_key, tokens) appropriately
3. avoid localization gaps for primary user-facing metadata
4. keep generated capability declarations aligned with runtime behavior

Source References

• Manifest Spec - User Configuration
• Manifest Spec - Tools and Prompts
• Manifest Spec - Localization

Summary

You now have a configuration and localization strategy for robust bundle UX.

Next: Chapter 5: CLI Workflows: Init, Validate, and Pack

Source Code Walkthrough

src/cli/init.ts

The promptLongDescription function in src/cli/init.ts handles a key part of this chapter's functionality:

}

export async function promptLongDescription(description: string) {
  const hasLongDescription = await confirm({
    message: "Add a detailed long description?",
    default: false,
  });

  if (hasLongDescription) {
    const longDescription = await input({
      message: "Long description (supports basic markdown):",
      default: description,
    });
    return longDescription;
  }

  return undefined;
}

export async function promptUrls() {
  const homepage = await input({
    message: "Homepage URL (optional):",
    validate: (value) => {
      if (!value.trim()) return true;
      try {
        new URL(value);
        return true;
      } catch {
        return "Must be a valid URL (e.g., https://example.com)";
      }
    },
  });

This function is important because it defines how MCPB Tutorial: Packaging and Distributing Local MCP Servers as Bundles implements the patterns covered in this chapter.

src/cli/init.ts

The promptUrls function in src/cli/init.ts handles a key part of this chapter's functionality:

}

export async function promptUrls() {
  const homepage = await input({
    message: "Homepage URL (optional):",
    validate: (value) => {
      if (!value.trim()) return true;
      try {
        new URL(value);
        return true;
      } catch {
        return "Must be a valid URL (e.g., https://example.com)";
      }
    },
  });

  const documentation = await input({
    message: "Documentation URL (optional):",
    validate: (value) => {
      if (!value.trim()) return true;
      try {
        new URL(value);
        return true;
      } catch {
        return "Must be a valid URL";
      }
    },
  });

  const support = await input({
    message: "Support URL (optional):",
    validate: (value) => {

This function is important because it defines how MCPB Tutorial: Packaging and Distributing Local MCP Servers as Bundles implements the patterns covered in this chapter.

src/cli/init.ts

The promptVisualAssets function in src/cli/init.ts handles a key part of this chapter's functionality:

}

export async function promptVisualAssets() {
  const icon = await input({
    message: "Icon file path (optional, relative to manifest):",
    validate: (value) => {
      if (!value.trim()) return true;
      if (value.includes("..")) return "Relative paths cannot include '..'";
      return true;
    },
  });

  const addIconVariants = await confirm({
    message: "Add theme/size-specific icons array?",
    default: false,
  });

  const icons: Array<{
    src: string;
    size: string;
    theme?: string;
  }> = [];

  if (addIconVariants) {
    let addMoreIcons = true;
    while (addMoreIcons) {
      const iconSrc = await input({
        message: "Icon source path (relative to manifest):",
        validate: (value) => {
          if (!value.trim()) return "Icon path is required";
          if (value.includes("..")) return "Relative paths cannot include '..'";
          return true;

This function is important because it defines how MCPB Tutorial: Packaging and Distributing Local MCP Servers as Bundles implements the patterns covered in this chapter.

src/cli/init.ts

The promptLocalization function in src/cli/init.ts handles a key part of this chapter's functionality:

}

export async function promptLocalization() {
  const configureLocalization = await confirm({
    message: "Configure localization resources?",
    default: false,
  });

  if (!configureLocalization) {
    return undefined;
  }

  const placeholderRegex = /\$\{locale\}/i;

  const resourcesPath = await input({
    message:
      "Localization resources path (must include ${locale} placeholder):",
    default: "resources/${locale}.json",
    validate: (value) => {
      if (!value.trim()) {
        return "Resources path is required";
      }
      if (value.includes("..")) {
        return "Relative paths cannot include '..'";
      }
      if (!placeholderRegex.test(value)) {
        return "Path must include a ${locale} placeholder";
      }
      return true;
    },
  });

This function is important because it defines how MCPB Tutorial: Packaging and Distributing Local MCP Servers as Bundles implements the patterns covered in this chapter.

How These Components Connect

flowchart TD
    A[promptLongDescription]
    B[promptUrls]
    C[promptVisualAssets]
    D[promptLocalization]
    E[promptCompatibility]
    A --> B
    B --> C
    C --> D
    D --> E

Loading