---
title: "MCP capability primitives · agent building block · Agent Fieldbook"
url: https://agentfieldbook.org/design/building_blocks/mcp-primitives/
description: "A fixed vocabulary of capability types, Tools, Resources, Prompts, Sampling, Elicitation, Roots, each with JSON-RPC methods (tools/call, resources/read, prompts/get…). The shared ontology of what a server can offer an agent."
section: "Design · Building Blocks · Ontology"
source: Agent Fieldbook — generated from the published page
---

# MCP capability primitives

A fixed vocabulary of capability types, Tools, Resources, Prompts, Sampling, Elicitation, Roots, each with JSON-RPC methods (tools/call, resources/read, prompts/get…). The shared ontology of what a server can offer an agent.

## How it works

## At a glance

| Field | Value |
| --- | --- |
| Kind | Ontology· Protocol primitives |
| Example | Model Context Protocol |

## Basis

- [modelcontextprotocol.io](https://modelcontextprotocol.io/specification)