MCP review

Overview

• Tools: Model controlled
• Resources: App controlled
• Prompts: User controlled

Tools

• Claude/the model decides when to run tools
• Used to add capabilities to Claude
• Implement tools in your MCP server or consume them through your MCP client
• Example: JavaScript code execution triggered by the model's decision

Resources

• Application code decides when to fetch resources
• Used to get data into your app for UI display or content rendering
• Implement resources in your MCP server
• Example: Fetching autocomplete options or augmenting prompts with data

Prompts

• Users decide when prompts run (via buttons, menu options, slash commands, etc. )
• Used to implement predefined workflows
• Implement prompts in your MCP server
• Example: Pre-written, optimized workflows available to users

Purpose Summary

• Tools serve the model
• Resources serve the app
• Prompts serve the users

When to Use Each

• Need to add model capabilities → implement tools
• Need to display data in UI → use resources
• Need predefined user workflows → use prompts

Takeaways

• Tools are model-controlled capabilities; Resources are app-controlled data; Prompts are user-controlled workflows
• Tools add capabilities to Claude; Resources get data into your app for UI display; Prompts implement predefined workflows
• Choose tools for model capabilities, resources for UI data display, and prompts for user-triggered workflows