Tools & MCP — Glossary
Tool Design & MCP Integration · 18% of the exam. 10 terms.
Tool schema
The JSON Schema describing a tool's name, description, and input parameters that the model uses to decide when and how to call it.
Exam context: A vague tool description is a bigger source of exam-tested failures than a vague tool name.
tool_use block
The content block the model emits when it wants to call a tool: includes the tool name, a unique id, and structured input.
Exam context: Distinguish from tool_result, which is what the client sends back, not what the model sends.
tool_result block
The message the client returns containing a tool's output, matched to a tool_use id, optionally flagged is_error.
Exam context: Returning raw stack traces instead of a structured, actionable error is a textbook wrong answer.
Model Context Protocol (MCP)
An open protocol standardizing how AI applications connect to external tools, data sources, and prompt templates.
Exam context: Know the vocabulary precisely — MCP is tested on terminology, not just concept recognition.
MCP server / client / host
A server exposes tools, resources, and prompts; a client keeps a 1:1 connection to one server; a host is the application coordinating multiple clients.
Exam context: Claude Code is a host; each MCP server it connects to gets its own client connection.
MCP primitives
Tools (model-invoked actions), Resources (contextual data the app can read), and Prompts (reusable templates) exposed by a server.
Exam context: The exam distinguishes these by who invokes them: the model invokes tools; the user or app invokes resources and prompts.
Transport
How an MCP client and server communicate — stdio for a local subprocess, or Streamable HTTP for a remote server.
Exam context: Local, trusted integrations lean stdio; remote or shared servers need HTTP with its own auth story.
Structured error responses
Returning is_error: true with a clear, actionable message in a tool result so the model can self-correct.
Exam context: The exam rewards designs where a failed tool call gives the model enough signal to retry correctly, not just fail.
Tool distribution choice
Deciding whether a capability should be a built-in tool, an MCP server, or a slash command/skill — driven by who needs it and how often it changes.
Exam context: A capability only one project needs rarely justifies a standalone MCP server over a project-local skill.
Built-in tools
First-party tools like Bash, the text editor, and web search/fetch, usable without standing up an MCP server.
Exam context: Reach for a built-in tool before building custom infrastructure that duplicates one.