Model Drive Protocol

Expose runtime-local capabilities to AI agents - not just servers.

MDP is a bridge for capabilities that live inside active runtimes. Browsers, apps, local processes, IDE extensions, devices, and embedded runtimes can register structured paths with one MDP server, and MCP-compatible hosts can discover and invoke them through a stable bridge surface.

The Problem

Most agent integrations assume useful capabilities live in MCP servers.

In practice, the best context often lives somewhere else:

• browser tabs with user session, DOM, page state, and extensions

• IDEs with workspace files, editor selection, diagnostics, and commands

• local processes with CLI tools, background services, and private state

• mobile apps and device runtimes with sensors, permissions, and user context

These runtimes are not naturally MCP servers.

Without MDP, teams usually end up:

• rewriting runtime logic into standalone servers

• building one-off bridges for each host/runtime pair

• losing the live context that made the capability valuable

The Idea

MDP makes runtime capabilities discoverable as a path catalog.

/browser
  /tabs
    /active
      /dom
      /selection
      /actions/click

That runtime can be:

• Web

• Android

• iOS

• Qt / C++

• Node.js

• Python / Go / Rust / Java / Kotlin / C#

• native device or local agent processes

Each path can be discovered and invoked. The runtime keeps ownership of the actual capability, while the MDP server owns registration, routing, and MCP exposure.

The path model is the API. Clients register descriptors with expose(), and hosts discover or invoke them through listClients, listPaths, callPath, and callPaths.

Path-First, Skill-Aware

MDP does not flatten everything into a giant tool list. It supports endpoint paths, prompt paths, and skill paths:

• endpoint paths such as GET /search

• prompt paths that end with /prompt.md

• skill paths that end with /skill.md

Skills work well for progressive disclosure:

/workspace/review/skill.md
/workspace/review/files/skill.md
/workspace/review/files/diff

An agent can start at a high-level skill, then read deeper paths only when it needs more context.

Runtime -> MDP -> MCP

Browser / App / Device / Local Process
              |
              v
          MDP Client
              |
              v
          MDP Server
              |
              v
          MCP Host

Agents do not need to know where a capability lives. A browser tab, VSCode extension, local process, or device runtime can all appear through one unified bridge surface.

The core responsibilities stay separate:

• clients own capabilities

• the MDP server owns registration and routing

• MCP hosts talk to one fixed bridge surface

Why Not Just an MCP Server?

Because not every useful runtime should become a server.

Quick Example

Expose a browser selection path from a runtime client:

client.expose({
  path: '/browser/selection',
  description: 'Read the current browser selection.',
  handler: async () => ({ text: window.getSelection()?.toString() ?? '' })
})

The MCP host sees /browser/selection through the MDP bridge. The call still executes inside the live browser runtime.

What You Can Build

• AI coding agents with real IDE context

• browser-native agents without scraping workarounds

• mobile-aware and device-aware assistants

• local automation that keeps private runtime state local

• multi-agent systems sharing one runtime capability registry

• cross-device capability federation

Current Status

• protocol models for path descriptors, messages, errors, and guards

• TypeScript MDP server with MCP bridge tools

• JavaScript client SDK with browser bundle output

• ws / wss and http / https loop transports

• auth envelopes and transport-carried auth support

• GET /mdp/meta probing and optional upstream discovery

• optional node-local filesystem state snapshots under ./.mdp/store when enabled

• Chrome extension, VSCode extension, and browser simple client integrations

• primary-secondary server topology for layered local deployments

MDP is language-agnostic, but this repository currently ships the TypeScript/JavaScript reference implementation.

One Sentence

MDP is the missing layer between runtime-local capabilities and AI agents.

Architecture

At a high level, one user can work through different agent UIs such as Claude Code, Codex, or Cursor. Each UI talks to its own mdp server, those servers form a primary-secondary triangle, and all mdp clients connect only to the primary:

flowchart LR
  user["User"]

  subgraph agents["Agent UI"]
    claude["Claude Code"]
    codex["Codex"]
    cursor["Cursor"]
  end

  subgraph servers["MDP Server Federation"]
    primary["Primary MDP Server"]
    secondaryB["Secondary MDP Server B"]
    secondaryC["Secondary MDP Server C"]
  end

  clients["MDP Clients"]
  endpoints["Endpoints"]
  skills["Skills"]
  prompts["Prompts"]

  user --> claude
  user --> codex
  user --> cursor

  claude <-->|"local host link"| secondaryB
  codex <-->|"local host link"| primary
  cursor <-->|"local host link"| secondaryC

  primary <-->|"federation"| secondaryB
  primary <-->|"federation"| secondaryC
  secondaryB <-->|"federation"| secondaryC

  primary <-->|"client sessions"| clients
  clients --> endpoints
  clients --> skills
  clients --> prompts

One invocation can go directly to the primary server, or pass through a secondary server when one is present:

sequenceDiagram
  participant User
  participant Agent as AgentUI
  participant Secondary as Secondary Server
  participant Primary as Primary Server
  participant Client as MDP Client
  participant Runtime as Local Runtime

  User->>Agent: ask for an action
  opt AgentUI is attached to a secondary server
    Agent->>Secondary: call local mdp server
    Secondary->>Primary: federated request
  end
  opt AgentUI is attached directly to the primary server
    Agent->>Primary: call local mdp server
  end
  Primary->>Client: route MDP call
  Client->>Runtime: execute local logic
  Runtime-->>Client: result
  Client-->>Primary: callClientResult
  opt Result returns through a secondary server
    Primary-->>Secondary: federated result
    Secondary-->>Agent: tool result
  end
  opt Result returns directly to the primary-side AgentUI
    Primary-->>Agent: tool result
  end
  Agent-->>User: answer

Connection setup follows the same structure:

• each user connects to one AgentUI

• each AgentUI connects to its own colocated MDP server

• one MDP server becomes or is configured as the primary

• all runtime-local MDP clients open transports only to that primary server

• the primary forwards registry updates and routed messages to connected secondary servers

• if the primary server becomes unavailable, one secondary server should promote itself to the new primary and take over client-facing routing

Pick A Path

• Use Quick Start if you want the shortest path from zero to a working client plus MCP bridge.

• Use Server Tools and Server APIs if you already understand the model and need exact data formats.

• Use JavaScript SDK Quick Start if you want to embed MDP into a browser page, local process, or custom runtime.

• Use Go SDK, Python SDK, Rust SDK, JVM SDKs, or .NET SDK if you want a first-party runtime client outside JavaScript.

• Use Chrome Extension or VSCode Extension if you want a packaged runtime integration instead of wiring the SDK yourself.

What Is In This Repo

• packages/protocol: protocol models, message types, guards, and errors

• packages/server: MDP server runtime, transport server, and fixed MCP bridge

• packages/client: JavaScript client SDK and browser bundle

• sdks/python: Python client SDK

• sdks/go: Go client SDK

• sdks/rust: Rust client SDK

• sdks/jvm: Java and Kotlin client SDKs

• sdks/dotnet: C# client SDK

• apps/chrome-extension: packaged Chrome runtime integration

• apps/vscode-extension: packaged VSCode runtime integration

• docs: VitePress documentation site and Playground

Documentation

Use the docs for getting started, exact tool and API formats, and packaged integration guidance:

• Quick Start

• What Is MDP?

• Architecture

• Server Tools

• Server APIs

• JavaScript SDK Quick Start

• Go SDK Quick Start

• C# SDK Quick Start

• Chrome Extension

• VSCode Extension

• Playground

Contributing

For contributor workflow, release automation, maintainer setup, and CI internals, see CONTRIBUTING.md and docs/contributing.