--- title: "Glossary: MCP and act-layer terms | Agent MCP Directory" description: "41 terms for building and finding MCP servers, CLIs and agent surfaces, each defined briefly with a sourced example. From A2A to WebMCP." canonical: https://agentmcpdirectory.com/glossary site: "Agent MCP Directory" last_updated: 2026-11-04 section: "Glossary" --- # Glossary: MCP and act-layer terms | Agent MCP Directory > 41 terms for building and finding MCP servers, CLIs and agent surfaces, each defined briefly with a sourced example. From A2A to WebMCP. Source: https://agentmcpdirectory.com/glossary Site: Agent MCP Directory Last reviewed: 2026-11-04 # Glossary 41 terms used across this directory, from the act layer and MCP host to WebMCP and server cards. Each entry gives a one-line definition and an example with a source, so a reader and an agent can check the term against the specification it came from. | Act layer | The part of agent readiness about completing tasks: MCP servers, CLIs, APIs with OpenAPI, WebMCP and agent payments. | | --- | --- | | Agent Card | The A2A JSON document describing an agent's skills, endpoints and auth, served at /.well-known/agent-card.json. | | Agent Skills | A folder with a SKILL.md file of instructions and optional scripts that agents load on demand. | | Agent2Agent (A2A) | A protocol for agents to discover each other and exchange tasks, now at version 1.0.0. | | Agentic AI Foundation (AAIF) | The Linux Foundation-directed foundation that hosts MCP, A2A, goose and AGENTS.md. | | agents.json | An OpenAPI-based file at /.well-known/agents.json describing flows of API calls for agents. | | AI gateway | A proxy in front of model APIs that adds caching, rate limits, logs and billing across providers. | | Client ID Metadata Document (CIMD) | A JSON file on the client's domain whose HTTPS URL is used as the OAuth client_id, the recommended MCP registration method. | | Code Mode | A Cloudflare approach where the agent writes code against a typed API instead of calling many tools one by one, set by portal policy. | | Confused deputy | An attack where a proxy with its own credentials is tricked into acting for someone else; MCP security guidance addresses it for OAuth proxies. | | document.modelContext | The WebMCP entry point on the document object that holds registerTool, getTools and executeTool. | | Dynamic Client Registration (DCR) | RFC 7591 registration where a client POSTs to /register for credentials; deprecated in MCP 2026-07-28 and kept for compatibility. | | Elicitation | A way for a server to ask the user, through the client, for more information, now handled through multi round-trip requests. | | HTTP+SSE transport | The older MCP HTTP transport with a separate SSE endpoint, deprecated since 2025-03-26 and reclassified Deprecated in 2026-07-28. | | MCP Apps | An MCP extension in which a tool points to a ui:// resource the host renders as a sandboxed View. | | MCP client | The connector inside a host application that holds one connection to one MCP server. | | MCP gateway | A proxy in front of MCP servers that authenticates callers, injects upstream credentials, filters tools and logs calls. | | MCP host | The LLM application that starts client connections and asks the user for consent. | | MCP registry | A catalog of MCP server metadata that clients and directories read; the official one is registry.modelcontextprotocol.io. | | MCP server | A program that exposes tools, resources or prompts to MCP clients over stdio or Streamable HTTP. | | MCP server portal | Cloudflare's product that puts many MCP servers behind one authenticated endpoint with per-tool controls. | | mcp-publisher | The CLI that publishes a server.json to the official registry after namespace verification. | | Model Context Protocol (MCP) | A JSON-RPC 2.0 protocol in which hosts run clients that connect to servers offering tools, resources and prompts. | | Multi round-trip request (MRTR) | The 2026-07-28 pattern where a server returns input_required and the client retries the request with the answers. | | Namespace verification | Proof that a publisher controls a registry name, by GitHub login or OIDC for io.github names and DNS or HTTP for domains. | | NLWeb | Microsoft's open project giving sites a natural-language ask method with Schema.org JSON responses; each instance is an MCP server. | | Prompt | A templated message or workflow an MCP server offers to users. | | Protected Resource Metadata | The RFC 9728 document an MCP server MUST publish to name its authorization servers and scopes. | | Remote MCP server | An MCP server reached over the network, today through Streamable HTTP, rather than launched locally. | | Resource | Context or data an MCP server offers for the user or model to read, addressed by URI. | | Resource indicator | The RFC 8707 resource parameter that names the MCP server a token is for; clients MUST send it. | | server.json | The registry metadata file for one server: name, version, remotes, packages, website and repository. | | server/discover | The 2026-07-28 RPC every server MUST implement to advertise supported protocol versions, capabilities and identity. | | Stateless MCP | The 2026-07-28 model with no initialize handshake and no Mcp-Session-Id; each request carries version and capabilities in _meta. | | stdio transport | The MCP binding where a client launches the server as a subprocess and exchanges newline-delimited JSON-RPC over standard streams. | | Step-up authorization | Requesting a wider scope set after a 403 insufficient_scope challenge, keeping previously granted scopes. | | Streamable HTTP | The MCP HTTP binding where each message is a POST to one endpoint and replies come as JSON or a request-scoped SSE stream. | | Tasks extension | An official MCP extension for long-running operations with polling and durable handles, moved out of core in 2026-07-28. | | Tool | A function an MCP server offers for the model to call, with a name, description and input schema. | | Tool annotations | Hints on a tool such as readOnlyHint and destructiveHint that tell clients how risky a call is. | | WebMCP | A draft browser API for pages to register JavaScript tools that an in-browser agent can call. | Edition 4 November 2026 Method [How rows are verified](https://agentmcpdirectory.com/method/) Data [CSV and JSON](https://agentmcpdirectory.com/data/) Markdown [This page as markdown](https://agentmcpdirectory.com/glossary/index.md) ## Sources - [Act layer](https://ora.ai/blog/agentready-launch?view=full&utm_source=agentmcpdirectory.com&utm_medium=referral&utm_campaign=index), read 4 November 2026 - [Agent Card](https://a2a-protocol.org/latest/specification/), read 4 November 2026 - [Agent Skills](https://docs.stripe.com/mcp), read 4 November 2026 - [Agent2Agent (A2A)](https://a2a-protocol.org/latest/blog/2026/08/27/a-new-chapter-for-a2a-joining-the-agentic-ai-foundation/), read 4 November 2026 - [agents.json](https://github.com/wild-card-ai/agents-json), read 4 November 2026 - [AI gateway](https://developers.cloudflare.com/ai-gateway/reference/pricing/), read 4 November 2026 - [Client ID Metadata Document (CIMD)](https://vercel.com/changelog/vercel-mcp-now-supports-client-id-metadata-documents), read 4 November 2026 - [Code Mode](https://developers.cloudflare.com/cloudflare-one/access-controls/ai-controls/mcp-portals/), read 4 November 2026 - [Confused deputy](https://vercel.com/docs/agent-resources/vercel-mcp), read 4 November 2026 - [document.modelContext](https://developers.cloudflare.com/changelog/post/2026-09-28-webmcp-api/), read 4 November 2026 - [Dynamic Client Registration (DCR)](https://supabase.com/docs/guides/getting-started/mcp), read 4 November 2026 - [Elicitation](https://modelcontextprotocol.io/specification/2025-11-25/changelog), read 4 November 2026 - [HTTP+SSE transport](https://developers.cloudflare.com/changelog/post/2026-10-22-cloudflare-mcp-servers-retire-sse/), read 4 November 2026 - [MCP Apps](https://vercel.com/changelog/monitor-vercel-deployments-in-chatgpt), read 4 November 2026 - [MCP gateway](https://portkey.ai/docs/product/mcp-gateway), read 4 November 2026 - [MCP host](https://modelcontextprotocol.io/specification/latest), read 4 November 2026 - [MCP registry](https://github.com/modelcontextprotocol/registry), read 4 November 2026 - [Multi round-trip request (MRTR)](https://modelcontextprotocol.io/specification/2026-07-28/changelog), read 4 November 2026 - [NLWeb](https://github.com/nlweb-ai/NLWeb), read 4 November 2026 - [Protected Resource Metadata](https://vercel.com/docs/mcp/deploy-mcp-servers-to-vercel), read 4 November 2026 - [Remote MCP server](https://registry.modelcontextprotocol.io/v0/servers), read 4 November 2026 - [Resource](https://www.mintlify.com/docs/ai/model-context-protocol), read 4 November 2026 - [Resource indicator](https://modelcontextprotocol.io/specification/2026-07-28/basic/authorization), read 4 November 2026 - [stdio transport](https://docs.apify.com/platform/integrations/mcp), read 4 November 2026 - [Step-up authorization](https://developers.cloudflare.com/changelog/post/2026-10-19-cloudflare-mcp-step-up/), read 4 November 2026 Last reviewed 4 November 2026