Merge pull request #234 from modelcontextprotocol/revert-233-docs/publishing-bundle-readme

Revert "docs: add "Publishing Your Bundle" section to README"

.github/workflows/test.yml

@@ -34,8 +34,37 @@ jobs:
           node-version: "${{ matrix.node-version }}"
           cache: "yarn"
       - name: Install dependencies
-        run: yarn install --frozen-lockfile
+        run: yarn install --immutable
       - name: Build
         run: yarn build
       - name: Test
         run: yarn lint && yarn test
+
+  validate-schemas:
+    name: Validate JSON Schemas
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+      - name: Setup Node.js
+        uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4.4.0
+        with:
+          node-version: "22.17.x"
+          cache: "yarn"
+      - name: Install dependencies
+        run: yarn install --immutable
+      - name: Build code (required for schema generation)
+        run: yarn build:code
+      - name: Generate schemas
+        run: yarn build:schema
+      - name: Check for schema changes
+        run: |
+          if ! git diff --exit-code schemas/; then
+            echo "Error: JSON schemas in schemas/ directory are out of sync!"
+            echo "Please run 'yarn build:schema' and commit the changes."
+            echo ""
+            echo "Changes detected:"
+            git diff schemas/
+            exit 1
+          fi
+          echo "✓ All schemas are up to date"

.gitignore

@@ -88,6 +88,8 @@ typings/
 # Claude files
 .claude.json
 .claude/
+CLAUDE.md
+PROJECT_STATUS.md
 
 # Vite
 .vite/
@@ -105,4 +107,10 @@ self-signed-cert.pem
 self-signed-key.pem
 *.mcpb
 invalid-json.json
-**/server/lib/**
+**/server/lib/**
+
+# Rust example build artifacts
+examples/calculator-rust/target/
+examples/calculator-rust/server/
+
+.yarn/install-state.gz

.vscode/settings.json

@@ -6,5 +6,6 @@
   "eslint.validate": ["typescript"],
   "[typescript]": {
     "editor.defaultFormatter": "dbaeumer.vscode-eslint"
-  }
+  },
+  "typescript.tsdk": "node_modules/typescript/lib"
 }

.yarnrc.yml

@@ -0,0 +1,3 @@
+nodeLinker: node-modules
+
+yarnPath: .yarn/releases/yarn-4.10.3.cjs

CLI.md

@@ -292,7 +292,8 @@ MCPB uses PKCS#7 (Cryptographic Message Syntax) for digital signatures:
 ```
 [Original MCPB ZIP content]
 MCPB_SIG_V1
-[Base64-encoded PKCS#7 signature]
+[4-byte little-endian length prefix]
+[DER-encoded PKCS#7 signature]
 MCPB_SIG_END
 ```
 

CONTRIBUTING.md

@@ -0,0 +1,85 @@
+# Contributing to MCPB
+
+Thank you for your interest in contributing to MCPB! We welcome contributions from the community.
+
+## Getting Started
+
+1. Fork the repository
+2. Clone your fork: `git clone https://github.com/YOUR_USERNAME/mcpb.git`
+3. Install dependencies: `yarn`
+4. Build the project: `yarn build`
+5. Run tests: `yarn test`
+
+## Development Workflow
+
+1. Create a new branch for your feature or bugfix: `git checkout -b feature/your-feature-name`
+2. Make your changes
+3. Run linting: `yarn lint`
+4. Run tests to ensure everything passes: `yarn test`
+5. Commit your changes with a clear, descriptive commit message (all commits must be signed - see [Commit Signing](#commit-signing))
+6. Push to your fork and submit a pull request
+
+## Code Standards
+
+- **TypeScript**: All code should be written in TypeScript with proper type definitions
+- **Linting**: Run `yarn lint` before committing. Use `yarn fix` to auto-fix formatting issues
+- **Testing**: Add tests for new features and bug fixes
+- **Documentation**: Update relevant documentation (README.md, MANIFEST.md, etc.) when adding or changing functionality
+
+## Commit Signing
+
+**All commits must be signed.** This helps verify the authenticity of contributions.
+
+To set up commit signing, see [GitHub's documentation on commit signature verification](https://docs.github.com/en/authentication/managing-commit-signature-verification).
+
+## Pull Request Process
+
+1. Ensure your PR description clearly describes the problem and solution
+2. Reference any related issues in your PR description
+3. Make sure all tests pass and linting is clean
+4. Verify that all commits are signed
+5. Update documentation as needed
+6. Wait for review from maintainers
+
+## Types of Contributions
+
+### Bug Reports
+
+When filing a bug report, please include:
+
+- Clear description of the issue
+- Steps to reproduce
+- Expected vs actual behavior
+- Version information (`mcpb --version`)
+- Relevant logs or error messages
+
+### Feature Requests
+
+We welcome feature suggestions! Please:
+
+- Clearly describe the feature and use case
+- Explain why this would be valuable to users
+- Consider if it aligns with the project's goals
+
+### Code Contributions
+
+We especially welcome:
+
+- Bug fixes
+- Documentation improvements
+- Test coverage improvements
+- New features (please discuss in an issue first for large changes)
+
+## Testing
+
+- Write unit tests for new functionality
+- Ensure existing tests still pass
+- Test manually with real MCP bundles when applicable
+
+## Questions?
+
+Feel free to open an issue for questions about contributing or the project in general.
+
+## License
+
+By contributing to MCPB, you agree that your contributions will be licensed under the MIT License.

LICENSE

@@ -0,0 +1,216 @@
+The MCP project is undergoing a licensing transition from the MIT License to the Apache License, Version 2.0 ("Apache-2.0"). All new code and specification contributions to the project are licensed under Apache-2.0. Documentation contributions (excluding specifications) are licensed under CC-BY-4.0.
+
+Contributions for which relicensing consent has been obtained are licensed under Apache-2.0. Contributions made by authors who originally licensed their work under the MIT License and who have not yet granted explicit permission to relicense remain licensed under the MIT License.
+
+No rights beyond those granted by the applicable original license are conveyed for such contributions.
+
+---
+
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
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+
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+      transformation or translation of a Source form, including but
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+
+      "Work" shall mean the work of authorship, whether in Source or
+      Object form, made available under the License, as indicated by a
+      copyright notice that is included in or attached to the work
+      (an example is provided in the Appendix below).
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+      form, that is based on (or derived from) the Work and for which the
+      editorial revisions, annotations, elaborations, or other modifications
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+      of this License, Derivative Works shall not include works that remain
+      separable from, or merely link (or bind by name) to the interfaces of,
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+      "Contribution" shall mean any work of authorship, including
+      the original version of the Work and any modifications or additions
+      to that Work or Derivative Works thereof, that is intentionally
+      submitted to the Licensor for inclusion in the Work by the copyright
+      owner or by an individual or Legal Entity authorized to submit on behalf
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+      to the Licensor or its representatives, including but not limited to
+      communication on electronic mailing lists, source code control systems,
+      and issue tracking systems that are managed by, or on behalf of, the
+      Licensor for the purpose of discussing and improving the Work, but
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+      designated in writing by the copyright owner as "Not a Contribution."
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+      on behalf of whom a Contribution has been received by Licensor and
+      subsequently incorporated within the Work.
+
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+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
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+      Contribution(s) alone or by combination of their Contribution(s)
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+      institute patent litigation against any entity (including a
+      cross-claim or counterclaim in a lawsuit) alleging that the Work
+      or a Contribution incorporated within the Work constitutes direct
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+
+   4. Redistribution. You may reproduce and distribute copies of the
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+          Derivative Works a copy of this License; and
+
+      (b) You must cause any modified files to carry prominent notices
+          stating that You changed the files; and
+
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+
+      (d) If the Work includes a "NOTICE" text file as part of its
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+          include a readable copy of the attribution notices contained
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+          as part of the Derivative Works; within the Source form or
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+          wherever such third-party notices normally appear. The contents
+          of the NOTICE file are for informational purposes only and
+          do not modify the License. You may add Your own attribution
+          notices within Derivative Works that You distribute, alongside
+          or as an addendum to the NOTICE text from the Work, provided
+          that such additional attribution notices cannot be construed
+          as modifying the License.
+
+      You may add Your own copyright statement to Your modifications and
+      may provide additional or different license terms and conditions
+      for use, reproduction, or distribution of Your modifications, or
+      for any such Derivative Works as a whole, provided Your use,
+      reproduction, and distribution of the Work otherwise complies with
+      the conditions stated in this License.
+
+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
+      this License, without any additional terms or conditions.
+      Notwithstanding the above, nothing herein shall supersede or modify
+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
+
+   6. Trademarks. This License does not grant permission to use the trade
+      names, trademarks, service marks, or product names of the Licensor,
+      except as required for reasonable and customary use in describing the
+      origin of the Work and reproducing the content of the NOTICE file.
+
+   7. Disclaimer of Warranty. Unless required by applicable law or
+      agreed to in writing, Licensor provides the Work (and each
+      Contributor provides its Contributions) on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+      implied, including, without limitation, any warranties or conditions
+      of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+      PARTICULAR PURPOSE. You are solely responsible for determining the
+      appropriateness of using or redistributing the Work and assume any
+      risks associated with Your exercise of permissions under this License.
+
+   8. Limitation of Liability. In no event and under no legal theory,
+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
+      liable to You for damages, including any direct, indirect, special,
+      incidental, or consequential damages of any character arising as a
+      result of this License or out of the use or inability to use the
+      Work (including but not limited to damages for loss of goodwill,
+      work stoppage, computer failure or malfunction, or any and all
+      other commercial damages or losses), even if such Contributor
+      has been advised of the possibility of such damages.
+
+   9. Accepting Warranty or Additional Liability. While redistributing
+      the Work or Derivative Works thereof, You may choose to offer,
+      and charge a fee for, acceptance of support, warranty, indemnity,
+      or other liability obligations and/or rights consistent with this
+      License. However, in accepting such obligations, You may act only
+      on Your own behalf and on Your sole responsibility, not on behalf
+      of any other Contributor, and only if You agree to indemnify,
+      defend, and hold each Contributor harmless for any liability
+      incurred by, or claims asserted against, such Contributor by reason
+      of your accepting any such warranty or additional liability.
+
+   END OF TERMS AND CONDITIONS
+
+---
+
+MIT License
+
+Copyright (c) 2024-2025 Model Context Protocol a Series of LF Projects, LLC.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+
+---
+
+Creative Commons Attribution 4.0 International (CC-BY-4.0)
+
+Documentation in this project (excluding specifications) is licensed under
+CC-BY-4.0. See https://creativecommons.org/licenses/by/4.0/legalcode for
+the full license text.

LICENSE.md

@@ -1,7 +0,0 @@
-Copyright 2025 Anthropic, PBC.
-
-Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
-
-The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

MANIFEST.md

@@ -1,7 +1,7 @@
 # MCPB Manifest.json Spec
 
-Current version: `0.2`
-Last updated: 2025-09-12
+Current version: `0.3`
+Last updated: 2025-12-02
 
 ## Manifest Schema
 
@@ -9,15 +9,15 @@ The `manifest.json` file contains all extension metadata and configuration. Most
 
 A basic `manifest.json` with just the required fields looks like this:
 
-```json
+```jsonc
 {
-  "manifest_version": "0.2", // Manifest spec version this manifest conforms to
+  "manifest_version": "0.3", // Manifest spec version this manifest conforms to
   "name": "my-extension", // Machine-readable name (used for CLI, APIs)
   "version": "1.0.0", // Semantic version of your extension
   "description": "A simple MCP extension", // Brief description of what the extension does
   "author": {
     // Author information (required)
-    "name": "Extension Author" // Author's name (required field)
+    "name": "Extension Author", // Author's name (required field)
   },
   "server": {
     // Server configuration (required)
@@ -28,16 +28,16 @@ A basic `manifest.json` with just the required fields looks like this:
       "command": "node", // Command to run the server
       "args": [
         // Arguments passed to the command
-        "${__dirname}/server/index.js" // ${__dirname} is replaced with the extension's directory
-      ]
-    }
-  }
+        "${__dirname}/server/index.js", // ${__dirname} is replaced with the extension's directory
+      ],
+    },
+  },
 }
 ```
 
 ```json
 {
-  "manifest_version": "0.2",
+  "manifest_version": "0.3",
   "name": "my-extension",
   "version": "1.0.0",
   "description": "A simple MCP extension",
@@ -71,7 +71,7 @@ A full `manifest.json` with most of the optional fields looks like this:
 
 ```json
 {
-  "manifest_version": "0.1",
+  "manifest_version": "0.3",
   "name": "My MCP Extension",
   "display_name": "My Awesome MCP Extension",
   "version": "1.0.0",
@@ -84,16 +84,32 @@ A full `manifest.json` with most of the optional fields looks like this:
   },
   "repository": {
     "type": "git",
-    "url": "https://github.com/your-username/my-mcp-extension"
+    "url": "https://github.com/your-username/my-mcp-extension.git"
   },
   "homepage": "https://example.com/my-extension",
   "documentation": "https://docs.example.com/my-extension",
   "support": "https://github.com/your-username/my-extension/issues",
   "icon": "icon.png",
+  "icons": [
+    {
+      "src": "assets/icons/icon-16-light.png",
+      "size": "16x16",
+      "theme": "light"
+    },
+    {
+      "src": "assets/icons/icon-16-dark.png",
+      "size": "16x16",
+      "theme": "dark"
+    }
+  ],
   "screenshots": [
     "assets/screenshots/screenshot1.png",
     "assets/screenshots/screenshot2.png"
   ],
+  "localization": {
+    "resources": "custom-directory-for-mcpb-resources/${locale}.json",
+    "default_locale": "en-US"
+  },
   "server": {
     "type": "node",
     "entry_point": "server/index.js",
@@ -155,6 +171,54 @@ A full `manifest.json` with most of the optional fields looks like this:
       "min": 1,
       "max": 100
     }
+  },
+  "_meta": {
+    "com.microsoft.windows": {
+      "package_family_name": "MyMcpMSIXPackage_51g09708xawrw",
+      "static_responses": {
+        "initialize": {
+          "capabilities": {},
+          "instructions": "When the user wants to search files, use the search_files tool but only after asking them whether the files are local.",
+          "protocolVersion": "2025-06-18",
+          "serverInfo": {
+            "name": "MyMCPExtension",
+            "title": "My MCP Extension - Pro Edition",
+            "version": "1.0.0"
+          }
+        },
+        "tools/list": {
+          "tools": [
+            {
+              "name": "search_files",
+              "title": "File search",
+              "description": "Search for files in a directory",
+              "inputSchema": {
+                "type": "object",
+                "properties": {
+                  "fileSpec": {
+                    "type": "string",
+                    "description": "The file name to search for. Wildcards are supported"
+                  }
+                },
+                "required": ["fileSpec"]
+              },
+              "outputSchema": {
+                "type": "object",
+                "properties": {
+                  "searchResults": {
+                    "type": "array",
+                    "description": "The list of file paths that were found",
+                    "items": {
+                      "type": "string"
+                    }
+                  }
+                }
+              }
+            }
+          ]
+        }
+      }
+    }
   }
 }
 ```
@@ -166,29 +230,72 @@ A full `manifest.json` with most of the optional fields looks like this:
 - **manifest_version**: Specification version this extension conforms to
 - **name**: Machine-readable name (used for CLI, APIs)
 - **version**: Semantic version (semver)
-- **description**: Brief description
-- **author**: Author information object with name (required), email (optional), and url (optional)
+- 🌎 **description**: Brief description. This field is localizable.
+- 🌎 **author**: Author information object with name (required, localizable), email (optional), and url (optional)
 - **server**: Server configuration object
 
 ### Optional Fields
 
-- **icon**: Path to a png icon file, either relative in the package or a https:// url.
-- **display_name**: Human-friendly name for UI display
-- **long_description**: Detailed description for extension stores, markdown
-- **repository**: Source code repository information (type and url)
-- **homepage**: Extension homepage URL
-- **documentation**: Documentation URL
-- **support**: Support/issues URL
-- **screenshots**: Array of screenshot paths
-- **tools**: Array of tools the extension provides
-- **tools_generated**: Boolean indicating the server generates additional tools at runtime (default: false)
-- **prompts**: Array of prompts the extension provides
-- **prompts_generated**: Boolean indicating the server generates additional prompts at runtime (default: false)
-- **keywords**: Search keywords
-- **license**: License identifier
-- **privacy_policies**: Array of URLs to privacy policies for external services that handle user data. Required when the extension connects to external services (first- or third-party) that process user data. Each URL should link to the respective service's privacy policy document
-- **compatibility**: Compatibility requirements (client app version, platforms, and runtime versions)
-- **user_config**: User-configurable options for the extension (see User Configuration section)
+- **icon**: Path to a png icon file, either relative in the package or a `https://` url.
+- **icons**: Array of icon descriptors (`src`, `size`, optional `theme`) for light/dark or size-specific assets.
+- 🌎 **display_name**: Human-friendly name for UI display. This field is localizable.
+- 🌎 **long_description**: Detailed description for extension stores, markdown. This field is localizable.
+- **repository**: Source code repository information (type and url).
+- **homepage**: Extension homepage URL.
+- **documentation**: Documentation URL.
+- **support**: Support/issues URL.
+- **screenshots**: Array of screenshot paths.
+- 🌎 **tools**: Array of tools the extension provides. This field is localizable.
+- **tools_generated**: Boolean indicating the server generates additional tools at runtime (default: false).
+- 🌎 **prompts**: Array of prompts the extension provides. This field is localizable.
+- **prompts_generated**: Boolean indicating the server generates additional prompts at runtime (default: false).
+- 🌎 **keywords**: Search keywords. This field is localizable.
+- **license**: License identifier.
+- **privacy_policies**: Array of URLs to privacy policies for external services that handle user data. Required when the extension connects to external services (first- or third-party) that process user data. Each URL should link to the respective service's privacy policy document.
+- **compatibility**: Compatibility requirements (client app version, platforms, and runtime versions).
+- **user_config**: User-configurable options for the extension (see User Configuration section).
+- **\_meta**: Platform-specific client integration metadata (e.g., Windows `package_family_name`, macOS bundle identifiers) enabling tighter OS/app store integration. The keys in the `_meta` object are reverse-DNS namespaced, and the values are a dictionary of platform-specific metadata.
+- **localization**: Location of translated strings for user-facing fields (`resources` path containing a `${locale}` placeholder and `default_locale`).
+
+### Localization
+
+Provide localized strings without bloating the manifest by pointing to external per-locale resource files. A localization entry looks like this:
+
+```jsonc
+"localization": {
+  "resources": "relative-path-to-resources/${locale}.json",
+  "default_locale": "en-US"
+}
+```
+
+- `resources` must include a `${locale}` placeholder. Clients resolve it relative to the server install directory.
+  - This property is optional, and its default value is **`mcpb-resources/${locale}.json`**.
+- `default_locale` must be a valid [BCP 47](https://www.rfc-editor.org/rfc/bcp/bcp47.txt) identifier such as `en-US` or `zh-Hans`.
+  - This property is optional, and its default value is `en-US`.
+- Values for the default locale stay in the main manifest; localized files only need to contain overrides.
+
+For tools and prompts, the descriptions are also localizable.
+
+#### Client guidelines
+
+- if a client wants to show tool or prompt descriptions in their UI, the client should look for the locale-specific description override in the corresponding per-locale file.
+- clients should only look for tools/prompts present in the manifest.json, i.e. prompts and tools that only exist in the per-locale file should be ignored.
+- Clients should apply locale fallbacks if the client/user locale is not represented by the server. For example, if the user is in the `es-UY` locale but the server does not include that per-locale file, the client should look for an approrpiate fallback, e.g. `es-MX` or `es-ES`, or fall back to the values in the manifest.
+
+### Icons
+
+Use the `icons` array when you need multiple icon variants (different sizes or themes):
+
+```json
+"icons": [
+  { "src": "assets/icons/icon-16-light.png", "size": "16x16", "theme": "light" },
+  { "src": "assets/icons/icon-16-dark.png", "size": "16x16", "theme": "dark" }
+]
+```
+
+- `size` must be in `WIDTHxHEIGHT` form (e.g., `128x128`).
+- `theme` is optional; use values like `light`, `dark`, or platform-specific labels (e.g., `high-contrast`).
+- The legacy `icon` field remains supported for single assets—clients use it when `icons` is omitted.
 
 ## Compatibility
 
@@ -291,6 +398,53 @@ The `server` object defines how to run the MCP server:
 
 ### Server Types
 
+Four server types are supported:
+
+- **`node`**: Node.js server with bundled dependencies
+- **`python`**: Python server with bundled dependencies
+- **`binary`**: Compiled executable
+- **`uv`**: Python server using UV runtime (v0.4+)
+
+### UV Runtime (v0.4+)
+
+The `uv` server type enables cross-platform Python extensions without bundling dependencies. Instead, dependencies are declared in `pyproject.toml` and installed by the host application using UV.
+
+**Benefits:**
+- Cross-platform support (Windows, macOS, Linux; Intel, ARM)
+- Small bundle size (~100 KB vs 5-10 MB)
+- Handles compiled dependencies (pydantic, numpy, etc.)
+- No user Python installation required
+
+**Example:**
+```json
+{
+  "manifest_version": "0.4",
+  "server": {
+    "type": "uv",
+    "entry_point": "src/server.py"
+  }
+}
+```
+
+**Requirements:**
+- Must include `pyproject.toml` with dependencies
+- Must NOT include `server/lib/` or `server/venv/`
+- `mcp_config` is optional (host manages execution)
+
+**Package structure:**
+```
+extension.mcpb
+├── manifest.json       # server.type = "uv"
+├── pyproject.toml      # Dependencies
+├── .mcpbignore        # Exclude .venv, server/lib
+└── src/
+    └── server.py
+```
+
+See `examples/hello-world-uv` for a complete example.
+
+### Node, Python, and Binary Types
+
 1. **Python**: `server.type = "python"`
    - Requires `entry_point` to Python file
    - All dependencies must be bundled in the MCPB
@@ -557,9 +711,9 @@ For servers with a fixed set of capabilities, list them in arrays.
 Each prompt in the `prompts` array must include:
 
 - **name**: The identifier for the prompt
-- **description** (optional): Explanation of what the prompt does
+- 🌎 **description** (optional): Explanation of what the prompt does
 - **arguments** (optional): Array of argument names that can be used in the prompt text
-- **text**: The actual prompt text that uses template variables like `${arguments.topic}` or `${arguments.aspect}` as placeholders for MCP Client-supplied arguments. If your argument is named `language`, you'd add `${arguments.language} where you expect it to show up in the prompt.
+- 🌎 **text**: The actual prompt text that uses template variables like `${arguments.topic}` or `${arguments.aspect}` as placeholders for MCP Client-supplied arguments. If your argument is named `language`, you'd add `${arguments.language}` where you expect it to show up in the prompt.
 
 Example:
 

README.md

@@ -103,14 +103,28 @@ bundle.mcpb (ZIP file)
 └── icon.png              # Optional: Bundle icon
 ```
 
+### Language Choice Recommendation
+
+**We recommend implementing MCP servers in Node.js** rather than Python to reduce installation friction. Node.js ships with Claude for macOS and Windows, which means your bundle will work out-of-the-box for users without requiring them to install additional Python runtimes (or you to package them manually).
+
 ### Bundling Dependencies
 
-**Python Bundles:**
+**UV Runtime (v0.4+):**
 
+- Use `server.type = "uv"` in manifest
+- Include `pyproject.toml` with dependencies (no bundled packages needed)
+- Host application manages Python and dependencies automatically
+- Works cross-platform without user Python installation
+- See `examples/hello-world-uv`
+
+**Python Bundles (Traditional):**
+
+- Use `server.type = "python"` in manifest
 - Bundle all required packages in `server/lib/` directory
 - OR bundle a complete virtual environment in `server/venv/`
 - Use tools like `pip-tools`, `poetry`, or `pipenv` to create reproducible bundles
 - Set `PYTHONPATH` to include bundled packages via `mcp_config.env`
+- **Limitation**: Cannot portably bundle compiled dependencies (e.g., pydantic, which the MCP Python SDK requires)
 
 **Node.js Bundles:**
 
@@ -137,13 +151,13 @@ git clone https://github.com/anthropics/mcpb.git
 cd mcpb
 
 # Install dependencies
-npm install
+yarn
 
 # Build the project
-npm run build
+yarn build
 
 # Run tests
-npm test
+yarn test
 ```
 
 ## Release Process
@@ -155,4 +169,4 @@ npm test
 
 # License
 
-This project is licensed under the MIT License - see the [LICENSE](LICENSE) file for details.
+This project is licensed under the Apache License 2.0 for new contributions, with existing code under MIT - see the [LICENSE](LICENSE) file for details.

examples/README.md

@@ -14,11 +14,12 @@ But, the MCP servers themselves are not robust secure production ready servers a
 
 ## Examples Included
 
-| Example               | Type    | Demonstrates                             |
-| --------------------- | ------- | ---------------------------------------- |
-| `hello-world-node`    | Node.js | Basic MCP server with simple time tool   |
-| `chrome-applescript`  | Node.js | Browser automation via AppleScript       |
-| `file-manager-python` | Python  | File system operations and path handling |
+| Example               | Type    | Demonstrates                                |
+| --------------------- | ------- | ------------------------------------------- |
+| `hello-world-node`    | Node.js | Basic MCP server with simple time tool      |
+| `chrome-applescript`  | Node.js | Browser automation via AppleScript          |
+| `file-manager-python` | Python  | File system operations and path handling    |
+| `calculator-rust`     | Binary  | Compiled Rust binary as MCP Bundle          |
 
 ## Usage
 

examples/calculator-rust/.mcpbignore

@@ -0,0 +1,5 @@
+Cargo.toml
+Cargo.lock
+src/
+target/
+README.md

examples/calculator-rust/Cargo.toml

@@ -0,0 +1,18 @@
+[package]
+name = "mcp-calculator"
+version = "1.0.0"
+edition = "2024"
+
+[dependencies]
+rmcp = { version = "1.2.0", features = ["server", "macros", "transport-io", "schemars"] }
+tokio = { version = "1", features = ["macros", "rt-multi-thread", "io-std"] }
+serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
+anyhow = "1.0"
+tracing = "0.1"
+tracing-subscriber = { version = "0.3", features = ["env-filter", "std", "fmt"] }
+schemars = "1.0"
+
+[profile.release]
+strip = true
+lto = true

examples/calculator-rust/README.md

@@ -0,0 +1,73 @@
+# Calculator Rust Binary Example
+
+Demonstrates packaging a compiled Rust binary as an MCP Bundle using the `binary` server type. Based on the [official Rust MCP SDK calculator example](https://github.com/modelcontextprotocol/rust-sdk/tree/main/examples/servers).
+
+## What is Binary Server Type?
+
+Unlike `node` or `uv` server types where the source code is bundled and executed by a runtime, the `binary` server type packages a pre-compiled native executable. This is useful for:
+
+- Rust, Go, C/C++ MCP servers
+- Performance-sensitive workloads
+- Servers with no runtime dependencies
+
+The tradeoff is that binaries are platform-specific — you need a separate build for each target OS/architecture.
+
+## Structure
+
+```
+calculator-rust/
+├── manifest.json       # server.type = "binary"
+├── Cargo.toml          # Rust project
+├── .mcpbignore         # Exclude source from bundle
+└── src/
+    └── main.rs         # Calculator MCP server (~80 LOC)
+```
+
+After building, the `server/` directory is created with the compiled binary.
+
+## Building
+
+Requires [Rust](https://rustup.rs/) 1.85+.
+
+```bash
+cd examples/calculator-rust
+cargo build --release
+mkdir -p server
+cp target/release/mcp-calculator server/
+```
+
+## Packing
+
+```bash
+mcpb pack examples/calculator-rust
+```
+
+The `.mcpbignore` file excludes source code and build artifacts — only `manifest.json` and `server/mcp-calculator` end up in the bundle.
+
+## Testing
+
+```bash
+# MCP protocol handshake
+echo '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"test","version":"1.0"}}}' \
+  | ./server/mcp-calculator
+
+# Tool call
+(printf '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"test","version":"1.0"}}}\n'
+printf '{"jsonrpc":"2.0","method":"notifications/initialized"}\n'
+printf '{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"sum","arguments":{"a":3,"b":4}}}\n'
+sleep 1) | ./server/mcp-calculator
+```
+
+Expected: `sum(3, 4)` returns `{"text":"7"}`.
+
+## Tools
+
+- **sum** — Calculate the sum of two numbers
+- **sub** — Calculate the difference of two numbers
+
+## Notes
+
+- Binary size: ~2.5 MB (stripped, LTO enabled)
+- The `Cargo.toml` uses `edition = "2024"` (Rust 1.85+)
+- Logs are written to stderr via `tracing`, so they don't interfere with MCP's stdio transport
+- Uses the [rmcp](https://crates.io/crates/rmcp) crate (official Rust MCP SDK)

examples/calculator-rust/manifest.json

@@ -0,0 +1,36 @@
+{
+  "$schema": "../../dist/mcpb-manifest.schema.json",
+  "manifest_version": "0.3",
+  "name": "calculator-rust",
+  "display_name": "Calculator (Rust Binary)",
+  "version": "1.0.0",
+  "description": "A simple calculator MCP server compiled from Rust",
+  "long_description": "Demonstrates packaging a compiled Rust binary as an MCP Bundle using the binary server type. The server provides sum and sub tools for basic arithmetic. Based on the official Rust MCP SDK calculator example.",
+  "author": {
+    "name": "Model Context Protocol"
+  },
+  "server": {
+    "type": "binary",
+    "entry_point": "server/mcp-calculator",
+    "mcp_config": {
+      "command": "${__dirname}/server/mcp-calculator",
+      "args": [],
+      "env": {}
+    }
+  },
+  "tools": [
+    {
+      "name": "sum",
+      "description": "Calculate the sum of two numbers"
+    },
+    {
+      "name": "sub",
+      "description": "Calculate the difference of two numbers"
+    }
+  ],
+  "keywords": ["calculator", "rust", "binary", "example"],
+  "license": "Apache-2.0",
+  "compatibility": {
+    "platforms": ["darwin", "linux"]
+  }
+}

examples/calculator-rust/src/main.rs

@@ -0,0 +1,80 @@
+use anyhow::Result;
+use rmcp::{
+    ServerHandler, ServiceExt,
+    handler::server::{router::tool::ToolRouter, wrapper::Parameters},
+    model::{ServerCapabilities, ServerInfo},
+    schemars, tool, tool_handler, tool_router,
+    transport::stdio,
+};
+use tracing_subscriber::{self, EnvFilter};
+
+// --- Calculator types ---
+
+#[derive(Debug, serde::Deserialize, schemars::JsonSchema)]
+pub struct SumRequest {
+    #[schemars(description = "the left hand side number")]
+    pub a: i32,
+    pub b: i32,
+}
+
+#[derive(Debug, serde::Deserialize, schemars::JsonSchema)]
+pub struct SubRequest {
+    #[schemars(description = "the left hand side number")]
+    pub a: i32,
+    #[schemars(description = "the right hand side number")]
+    pub b: i32,
+}
+
+// --- Calculator server ---
+
+#[derive(Debug, Clone)]
+pub struct Calculator {
+    tool_router: ToolRouter<Self>,
+}
+
+#[tool_router]
+impl Calculator {
+    pub fn new() -> Self {
+        Self {
+            tool_router: Self::tool_router(),
+        }
+    }
+
+    #[tool(description = "Calculate the sum of two numbers")]
+    fn sum(&self, Parameters(SumRequest { a, b }): Parameters<SumRequest>) -> String {
+        (a + b).to_string()
+    }
+
+    #[tool(description = "Calculate the difference of two numbers")]
+    fn sub(&self, Parameters(SubRequest { a, b }): Parameters<SubRequest>) -> String {
+        (a - b).to_string()
+    }
+}
+
+#[tool_handler]
+impl ServerHandler for Calculator {
+    fn get_info(&self) -> ServerInfo {
+        ServerInfo::new(ServerCapabilities::builder().enable_tools().build())
+            .with_instructions("A simple calculator".to_string())
+    }
+}
+
+// --- Main ---
+
+#[tokio::main]
+async fn main() -> Result<()> {
+    tracing_subscriber::fmt()
+        .with_env_filter(EnvFilter::from_default_env().add_directive(tracing::Level::DEBUG.into()))
+        .with_writer(std::io::stderr)
+        .with_ansi(false)
+        .init();
+
+    tracing::info!("Starting Calculator MCP server");
+
+    let service = Calculator::new().serve(stdio()).await.inspect_err(|e| {
+        tracing::error!("serving error: {:?}", e);
+    })?;
+
+    service.waiting().await?;
+    Ok(())
+}

examples/chrome-applescript/server/index.js

@@ -33,17 +33,6 @@ class ChromeControlServer {
     this.setupHandlers();
   }
 
-  // Helper methods
-  escapeForAppleScript(str) {
-    if (typeof str !== "string") return str;
-    // Basic AppleScript string escaping
-    return str
-      .replace(/\\/g, "\\\\") // Escape backslashes first
-      .replace(/"/g, '\\"') // Then escape double quotes
-      .replace(/\n/g, "\\n") // Escape newlines
-      .replace(/\r/g, "\\r"); // Escape carriage returns
-  }
-
   async checkChromeAvailable() {
     try {
       const script = 'tell application "Google Chrome" to return "available"';
@@ -82,12 +71,28 @@ class ChromeControlServer {
     }
   }
 
+  // Coerce tab_id to a safe numeric value before interpolating into
+  // AppleScript. inputSchema type:"number" is advisory — runtime may receive
+  // a string, which would otherwise be injected into the osascript template.
+  toSafeTabId(tabId) {
+    if (tabId === null || tabId === undefined) return null;
+    const n = Number.parseInt(tabId, 10);
+    if (Number.isNaN(n)) {
+      throw new Error("tab_id must be a number");
+    }
+    return n;
+  }
+
   async findTabById(tabId) {
+    const safeTabId = this.toSafeTabId(tabId);
+    if (safeTabId === null) {
+      return { w: null, t: null, found: false };
+    }
     const script = `
       tell application "Google Chrome"
         repeat with w in windows
           repeat with t in tabs of w
-            if (id of t as string) is "${tabId}" then
+            if (id of t as string) is "${safeTabId}" then
               return {w, t, true}
             end if
           end repeat
@@ -103,7 +108,8 @@ class ChromeControlServer {
     operation,
     successMessage = "Operation completed",
   ) {
-    if (!tabId) {
+    const safeTabId = this.toSafeTabId(tabId);
+    if (safeTabId === null) {
       // No tab ID, execute on active tab
       return this.executeAppleScript(operation.activeScript);
     }
@@ -112,7 +118,7 @@ class ChromeControlServer {
       tell application "Google Chrome"
         repeat with w in windows
           repeat with t in tabs of w
-            if (id of t as string) is "${tabId}" then
+            if (id of t as string) is "${safeTabId}" then
               ${operation.tabScript}
               return "${successMessage}"
             end if
@@ -272,10 +278,23 @@ class ChromeControlServer {
               throw new Error("URL is required and must be a string");
             }
 
-            const escapedUrl = this.escapeForAppleScript(url);
+            try {
+              new URL(url);
+            } catch (error) {
+              return {
+                content: [
+                  {
+                    type: "text",
+                    text: `Error: url is not a valid url - ${error.message}`,
+                  },
+                ],
+                isError: true,
+              };
+            }
+
             const script = new_tab
-              ? `tell application "Google Chrome" to open location "${escapedUrl}"`
-              : `tell application "Google Chrome" to set URL of active tab of front window to "${escapedUrl}"`;
+              ? `tell application "Google Chrome" to open location ${JSON.stringify(url)}`
+              : `tell application "Google Chrome" to set URL of active tab of front window to ${JSON.stringify(url)}`;
 
             await this.executeAppleScript(script);
             return {
@@ -551,6 +570,7 @@ class ChromeControlServer {
                 "JavaScript code is required and must be a string",
               );
             }
+            const safeTabId = this.toSafeTabId(tab_id);
 
             // Wrap the code to capture console.log outputs
             const wrappedCode = `
@@ -626,15 +646,14 @@ class ChromeControlServer {
               })();
             `;
 
-            const escapedCode = this.escapeForAppleScript(wrappedCode);
-
-            const script = tab_id
-              ? `
+            const script =
+              safeTabId != null
+                ? `
               tell application "Google Chrome"
                 repeat with w in windows
                   repeat with t in tabs of w
-                    if (id of t as string) is "${tab_id}" then
-                      set result to execute t javascript "${escapedCode}"
+                    if (id of t as string) is "${safeTabId}" then
+                      set result to execute t javascript ${JSON.stringify(wrappedCode)}
                       return result
                     end if
                   end repeat
@@ -642,9 +661,9 @@ class ChromeControlServer {
                 return "Tab not found"
               end tell
             `
-              : `
+                : `
               tell application "Google Chrome"
-                execute active tab of front window javascript "${escapedCode}"
+                execute active tab of front window javascript ${JSON.stringify(wrappedCode)}
               end tell
             `;
 
@@ -695,14 +714,16 @@ class ChromeControlServer {
 
           case "get_page_content": {
             const { tab_id } = args;
+            const safeTabId = this.toSafeTabId(tab_id);
 
             const jsCode = "document.body.innerText";
-            const script = tab_id
-              ? `
+            const script =
+              safeTabId != null
+                ? `
               tell application "Google Chrome"
                 repeat with w in windows
                   repeat with t in tabs of w
-                    if (id of t as string) is "${tab_id}" then
+                    if (id of t as string) is "${safeTabId}" then
                       set pageContent to execute t javascript "${jsCode}"
                       return pageContent
                     end if
@@ -711,7 +732,7 @@ class ChromeControlServer {
                 return "Tab not found"
               end tell
             `
-              : `
+                : `
               tell application "Google Chrome"
                 execute active tab of front window javascript "${jsCode}"
               end tell

examples/file-manager-python/.mcpbignore

@@ -0,0 +1,7 @@
+.venv/
+__pycache__/
+*.pyc
+.pytest_cache/
+.mypy_cache/
+*.egg-info/
+uv.lock

examples/file-manager-python/manifest.json

@@ -1,28 +1,28 @@
 {
-  "$schema": "../../dist/mcpb-manifest.schema.json",
-  "manifest_version": "0.1",
+  "manifest_version": "0.4",
   "name": "file-manager-python",
   "display_name": "Python File Manager MCP",
-  "version": "0.1.0",
+  "version": "0.2.0",
   "description": "A Python MCP server for file operations",
-  "long_description": "This extension provides file management capabilities through a Python MCP server. It demonstrates Python-based MCP Bundle development, including file operations, directory management, and proper MCP protocol implementation.",
+  "long_description": "This extension provides file management capabilities through a Python MCP server. It demonstrates Python-based MCP Bundle development using UV runtime, including file operations, directory management, and proper MCP protocol implementation.",
   "author": {
     "name": "Anthropic",
     "email": "support@anthropic.com",
     "url": "https://github.com/anthropics"
   },
   "server": {
-    "type": "python",
+    "type": "uv",
     "entry_point": "server/main.py",
     "mcp_config": {
-      "command": "python",
+      "command": "uv",
       "args": [
-        "${__dirname}/server/main.py",
+        "run",
+        "--directory", "${__dirname}",
+        "server/main.py",
         "--workspace=${user_config.workspace_directory}"
       ],
       "env": {
-        "DEBUG": "${user_config.debug_mode}",
-        "PYTHONPATH": "${__dirname}/server/lib"
+        "DEBUG": "${user_config.debug_mode}"
       }
     }
   },
@@ -62,8 +62,7 @@
     "claude_desktop": ">=0.10.0",
     "platforms": ["darwin", "win32", "linux"],
     "runtimes": {
-      "python": ">=3.8.0 <4"
+      "python": ">=3.10.0 <4"
     }
-  },
-  "privacy_policies": []
+  }
 }