| Agent |
A model running in a loop that chooses tools, observes results, and continues until the task is done. |
| Agent Skills standard |
The open, cross-vendor spec for SKILL.md folders (https://agentskills.io). Claude, Cursor, Codex, and others implement it. |
| AGENTS.md |
A plain Markdown instructions file at a repo’s root or in subfolders. It’s read by Cursor, Codex, and others, and it’s the vendor-neutral counterpart of CLAUDE.md. |
| Client (MCP) |
The component inside a host that holds one connection to one MCP server. |
| Context window |
The model’s working memory for a conversation. Everything you load (rules, skill bodies, tool schemas, file contents) competes for it. |
| Delegation |
A parent agent handing a task to a subagent. It’s driven by the subagent’s description. |
| Description |
The frontmatter text a model reads to decide whether to use a skill, subagent, or tool. It’s the single most important line you write. |
| Elicitation (MCP) |
A server asking the user for extra input partway through an operation, via the client. |
| Eval / eval set |
A fixed set of prompts with expected outcomes, used to measure whether a skill, agent, or tool behaves correctly and to catch regressions. |
| Frontmatter |
The YAML block between --- lines at the top of a Markdown file. |
| Hook |
A deterministic script run by the host on an agent event (before a tool call, after an edit, and so on). |
| Host (MCP) |
The application the user interacts with (Cursor, Claude Desktop, Claude Code) that runs MCP clients. |
| Inspector |
@modelcontextprotocol/inspector, the official interactive tester for MCP servers. |
| MCP |
The Model Context Protocol, an open JSON-RPC-based protocol for connecting AI hosts to tools and data. |
| MCPB |
MCP Bundle (.mcpb, formerly .dxt), a one-click installable package of a local MCP server for Claude Desktop. |
| Orchestrator |
An agent whose main job is to plan and delegate to other agents. |
| Progressive disclosure |
Loading information in stages. For a skill: metadata first, then the body when it’s relevant, then reference files only when they’re needed. |
| Prompt (MCP) |
A reusable, user-invoked message template that a server exposes. |
| Resource (MCP) |
Read-only data that a server exposes by URI (files, records, schemas). |
| Roots (MCP) |
Filesystem or URI boundaries a client tells a server it may operate within. |
| Sampling (MCP) |
A server asking the client’s model to generate a completion. |
| SDK agent |
An agent created and run from code (Claude Agent SDK, Cursor SDK) rather than from a chat UI. |
| Skill |
A folder containing SKILL.md (plus optional scripts, references, and assets) that packages a procedure or domain knowledge. |
| stdio transport |
MCP over a child process’s stdin/stdout. It’s used for local servers. stdout is reserved for protocol messages, so log to stderr. |
| Streamable HTTP |
The current MCP transport for remote servers: a single HTTP endpoint with optional SSE streaming. It replaces the older HTTP+SSE transport. |
| Subagent |
A child agent with its own prompt and context window. It returns a result to the parent. |
| Tool |
A function the model can call, with a name, description, and JSON Schema input. MCP servers expose tools; hosts have built-in tools too. |
| Tool annotations |
MCP hints about tool behaviour: readOnlyHint, destructiveHint, idempotentHint, openWorldHint. |
| Trigger |
The situation that should cause a skill or subagent to be used. It’s encoded in the description. |