[Repo] modelcontextprotocol/experimental-ext-interceptors: Status: Experimental. This repository provides a multi-language reference implementation of the proposed interceptor extension for the Model Context Protocol (MCP), as described in SEP-1763.

This experimental repository provides a multi-language reference implementation of the interceptor extension for the Model Context Protocol (MCP), as specified in SEP-1763. It demonstrates how to intercept and modify MCP protocol messages across different programming languages. The project is in early experimental status with active development, offering developers a foundation for building custom protocol interceptors.

Key Points

• •Experimental implementation of MCP interceptor extension (SEP-1763) for protocol message interception
• •Multi-language reference implementation supporting various programming languages
• •Enables custom message modification and filtering in MCP protocol flows
• •Primary language: C# with cross-language compatibility patterns
• •Active development with recent updates (March 2026)
• •Serves as reference architecture for building protocol-level interceptors
• •Foundational resource for extending MCP with custom middleware capabilities
• •Early-stage project suitable for research and experimental use cases

Workflow Diagram

Concepts