docs: Add GSoC 2026 Proposal - MCPApps Tester (MCPApps Tester — A Dedicated Testing & Debugging Environment for MCP Apps)

[ikeoffiah]

Description

This PR adds my initial idea submission for GSoC 2026 under the API Dash organization.

It proposes building MCPApps Tester, a dedicated web-based testing and debugging environment for MCP Apps. While other proposals under discussion #1225 focus on testing standard MCP backend primitives (Tools, Resources), this project addresses a major gap: the lack of tooling to validate the rich, interactive UI extensions of MCP servers.

By building this suite using React, Node, and TypeScript, the project aligns with the core MCP developer ecosystem and the tech stack preferences mentioned in the official GSoC discussion.

Key Highlights of the Proposal:

• Simulated Host & Handshake: Implements the full MCP Apps host protocol to validate ui/initialize sequences.
• Message Inspector: Provides a real-time, filterable stream of postMessage traffic between host and UI.
• Capability Mocking: Enables testing of UI behavior under various host restrictions (e.g., denying open_link or resize_iframe).
• End-to-End Tracing: Traces tools/call requests initiated from the UI all the way to the backend MCP server.
• Compliance Checker: Automated verification of protocol versioning, MIME types, and CSP safety.

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Related Issues

• Addresses Discussion on - MCP Testing Discussion on #1 - MCP Testing #1225
• References GSoC 2026: Application Guide GSoC 2026: Application Guide #1048

Checklist

• I have gone through the contributing guide
• I have updated my branch and synced it with project main
• I am using the latest node/npm versions
• All tests are passing (or verified against the proposal)

Added/updated tests?

• Yes
• No — This is an initial idea submission proposal document (no codebase changes yet).

OS

• macOS