Resources And Prompts

# Resources & Prompts — the other two primitives

MCP defines three server-side primitives. Tools are model-controlled (Claude decides when to call them). The other two are different:

- **Resources** are application-controlled — the host decides what to pull into context
- **Prompts** are user-controlled — surfaced as slash commands or menu items

Most servers only need tools. Reach for these when the shape of your integration doesn't fit "Claude calls a function."

---

## Resources

A resource is data identified by a URI. Unlike a tool, it's not *called* — it's *read*. The host browses available resources and decides which to load into context.

**When a resource beats a tool:**
- Large reference data (docs, schemas, configs) that Claude should be able to browse
- Content that changes independently of conversation (log files, live data)
- Anything where "Claude decides to fetch" is the wrong mental model

**When a tool is better:**
- The operation has side effects
- The result depends on parameters Claude chooses
- You want Claude (not the host UI) to decide when to pull it in

### Static resources