Model Context Protocol releases version 1.5, introducing dynamic resource template discovery and real-time tool list updates.

MCP Protocol Reaches 1.5: New Resource Templates and Tool Lists

Overview

Model Context Protocol (MCP) has released version 1.5, introducing several important improvements. As a standardized protocol for connecting AI models with external data and tools, MCP 1.5 significantly enhances dynamic discovery and real-time interaction capabilities.

New Features

1. Dynamic Resource Template Discovery

New resources/templates request allows clients to dynamically discover resource templates supported by servers:

// Client request
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "resources/templates/list",
  "params": {}
}

// Server response
{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "templates": [
      {
        "uriTemplate": "https://api.example.com/repos/{owner}/{repo}",
        "name": "Repository",
        "description": "A GitHub repository",
        "mimeType": "application/json"
      }
    ]
  }
}

2. Real-Time Tool List Updates

Improved tool registration mechanism supports dynamic add/remove of tools by servers:

{
  "jsonrpc": "2.0",
  "method": "notifications/tools/list_changed"
}

3. Enhanced Error Handling

New standardized error codes and detailed error information:

Error Code	Meaning
`-32600`	Invalid Request
`-32601`	Method Not Found
`-32602`	Invalid Params
`-32001`	Resource Not Found
`-32002`	Tool Execution Failed

4. Progress Tracking

New progress notification mechanism supports progress feedback for long-running operations:

{
  "jsonrpc": "2.0",
  "method": "notifications/progress",
  "params": {
    "progressToken": "abc123",
    "progress": 75,
    "total": 100,
    "message": "Processing..."
  }
}

Comparison with 1.4

Feature	MCP 1.4	MCP 1.5
Resource Template Discovery	❌	✅
Dynamic Tool Updates	Limited	✅ Full support
Error Handling	Basic	Standardized
Progress Tracking	❌	✅
Batch Operations	❌	✅

Impact on Developers

Server Developers

Implement resources/templates/list method for template discovery
Send notifications/tools/list_changed for tool changes
Use new error code format

Client Developers

Support dynamic resource template discovery
Handle tool list change notifications
Parse progress notifications

Ecosystem Updates

Major MCP servers have updated to 1.5:

GitHub MCP: Repository template discovery
PostgreSQL MCP: Dynamic table schema discovery
Sentry MCP: Real-time event streams
Linear MCP: Project template support