What are tools, resources and prompts in MCP?

Summary

Tools are actions the model can invoke (model-controlled), resources are data the application can read and add to context (application-controlled), and prompts are reusable templates that users or apps select (user-controlled).

Longer Answer

A search_tickets function is a tool; a ticket's contents at tickets://123 or a schema file is a resource; a "summarise this incident" template with arguments is a prompt. The split matters for control: tools need safety decisions because the model chooses to call them, while resources and prompts are chosen by the app or the user. Clients also offer capabilities to servers, such as sampling (letting a server request a model completion through the host) and elicitation (asking the user for input).

Key Points

• Tools: model-controlled actions.
• Resources: application-controlled data.
• Prompts: user-controlled templates.
• Clients can offer sampling and elicitation.