mcp-server-general

mcp-server-general

A general-purpose MCP server designed for long-running, plugin-driven AI orchestration.

This server is fully compatible with the MCP JSON-RPC specification and works seamlessly with:

• mcp-client-general – a general-purpose MCP CLI & programmatic client
  https://github.com/daporun/mcp-client-general

This repository implements a production-ready MCP server with:

• strict lifecycle management
• plugin-based extensibility
• protocol/lifecycle separation
• full test coverage

For plugin developers, see the Plugin Author Guide.

High-level Architecture

The MCP server is built from three strictly separated layers:

flowchart TD
    A[server.ts<br/>Bootstrap] --> B[MCPRuntime<br/>Lifecycle]
    B --> C[MCPServerLoop<br/>JSON-RPC Protocol]
    C --> D[MCPRouter & ListRegistry]

    subgraph Bootstrap
        A1[loadConfig]
        A2[loadPlugins]
        A3[buildHandshake]
        A4[runtime.onReady]
        A5[startMCPServer]
    end

    A --> A1
    A1 --> A2
    A2 --> A3
    A3 --> A4
    A4 --> A5
    A5 -->|start| C

    subgraph Lifecycle
        B1[onReady]
        B2[shutdown]
    end

    B --> B1
    B --> B2

    subgraph Protocol
        C1[STDIN JSON-RPC]
        C2[Router Dispatch]
        C3[STDOUT Response]
    end

    C --> C1 --> C2 --> C3

Why this separation matters

Protocol layer is stable
MCPServerLoop implements the MCP JSON-RPC contract and is validated against mcp-client-general.

Lifecycle is explicit and testable
MCPRuntime only manages startup and shutdown phases.

Plugins are isolated from transport details
Plugins never interact with STDIN / STDOUT directly.

This avoids the classic “god-runtime” anti-pattern and keeps each concern small and composable.

Server Startup Flow

The full startup sequence executed by server.ts:

loadConfig()
   ↓
loadPlugins()
   ├─ schema validation
   ├─ setup(ctx, config)
   └─ onInit(ctx)
   ↓
static registry setup (lists, core methods)
   ↓
buildHandshake()
   ↓
runtime.onReady()
   └─ plugin.onReady(ctx)
   ↓
startMCPServer()
   └─ long-running JSON-RPC loop

At the moment the MCP server loop starts, the system is fully initialized and in the READY state.

Plugin Lifecycle

Plugins follow a strict, deterministic lifecycle:

schema → setup → onInit → onReady → (runtime) → onShutdown

Lifecycle Hooks

schema (optional)

Declarative configuration validation using Zod.

setup(ctx, config) (optional)

Executed once after config validation.

Allowed

• Parsing
• Preparation
• Lightweight I/O

Not allowed

• Method registration

onInit(ctx) (optional)

Registration phase.

• Register MCP methods
• Register lists
• Wire runtime integrations

onReady(ctx) (optional)

Executed when the server is fully initialized.

• Warm-up logic
• Background tasks
• Health checks

Fail-fast
If any plugin throws here, server startup aborts.

onShutdown() (optional)

Graceful teardown on SIGINT / SIGTERM.

• Close connections
• Flush buffers
• Stop background work

Best-effort
Errors are logged but do not block other plugins.

Runtime Guarantees

MCPRuntime enforces the following invariants:

• onReady() runs at most once
• onShutdown() runs at most once
• onShutdown() continues even if a plugin fails
• onReady() is fail-fast
• Lifecycle hooks are fully covered by Vitest

Design Principles

Long-running server model There is no onFinished() hook by design. MCP servers run until terminated.

Context is explicit All lifecycle hooks that mutate runtime state receive MCPPluginContext.

Protocol ≠ Lifecycle MCP JSON-RPC handling is intentionally decoupled from lifecycle logic.

Getting Started

To interact with this server from the command line or from Node.js code, you can use:

• mcp-client-general
  A general-purpose MCP client with CLI and TypeScript API
  https://github.com/daporun/mcp-client-general

Summary

This architecture provides:

• Predictable startup and shutdown
• Stable MCP protocol handling
• Clean plugin extensibility
• High testability
• Clear mental model for contributors

It is intentionally minimal, but designed to scale.