MCP Bridge: A Lightweight, LLM-Agnostic RESTful Proxy for Model Context Protocol Servers

2025-04-11

AI Summary

Existing Model Context Protocol (MCP) implementations rely on STDIO-based local processes, limiting deployment on resource-constrained environments such as mobile devices, web browsers, and edge platforms. To address this, we propose a lightweight RESTful MCP proxy architecture. Our approach introduces an LLM-agnostic design, enabling unified integration of heterogeneous MCP backends via a novel STDIO-to-HTTP protocol bridge. We further propose a risk-aware three-tier execution model—standard, confirmation, and Docker-isolated—to ensure security and controllability while preserving backward compatibility with existing clients. The architecture supports dynamic backend registration, configurable security policies, and a natural-language interface compatible with Gemini Agent. Experimental evaluation demonstrates stable operation across web and edge devices; under Docker isolation, end-to-end latency remains below 200 ms. The solution significantly enhances cross-platform deployability and runtime security without compromising interoperability.

Technology Category

• Natural Language Processing: Safety and Robustness
• Machine Learning: Large Multimodal Models (LMMs)
• Multiagent Systems: Agent Communication

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Applied ML and AI for Web-based mobile applications
• Responsible Web: Machine-in-the-loop, human agency and autonomy
• Economics, Online Markets and Human Computation: Cost models of using LLMs in production systems

Abstract

Large Language Models (LLMs) are increasingly augmented with external tools through standardized interfaces like the Model Context Protocol (MCP). However, current MCP implementations face critical limitations: they typically require local process execution through STDIO transports, making them impractical for resource-constrained environments like mobile devices, web browsers, and edge computing. We present MCP Bridge, a lightweight RESTful proxy that connects to multiple MCP servers and exposes their capabilities through a unified API. Unlike existing solutions, MCP Bridge is fully LLM-agnostic, supporting any backend regardless of vendor. The system implements a risk-based execution model with three security levels standard execution, confirmation workflow, and Docker isolation while maintaining backward compatibility with standard MCP clients. Complementing this server-side infrastructure is a Python based MCP Gemini Agent that facilitates natural language interaction with MCP tools. The evaluation demonstrates that MCP Bridge successfully addresses the constraints of direct MCP connections while providing enhanced security controls and cross-platform compatibility, enabling sophisticated LLM-powered applications in previously inaccessible environments

Problem

• Enables MCP access in resource-limited environments like mobile and edge devices
• Provides a unified LLM-agnostic API for diverse backend MCP servers
• Introduces security tiers (standard/confirmation/Docker) for MCP tool execution

Innovation

• Lightweight RESTful proxy for MCP servers
• LLM-agnostic design supports any backend
• Risk-based execution model with three security levels