Architecture overview
Build clients
Develop applications that connect to MCP servers.
build-mcp-app skill
Adds interactive UI widgets rendered inline in chat.
Build MCP Apps
Build interactive apps that run inside AI clients.
build-mcp-server skill
Entry skill that interrogates the use case and routes to specialized skills.
build-mcpb skill
Packages a local stdio server with its runtime as a .mcpb archive.
Build servers
Create MCP servers to expose your data and tools.
Claude Desktop configuration
JSON config (claude_desktop_config.json) declaring servers to launch.
Concepts of MCP
Connect to any MCP server
MCP clients can connect to any MCP server.
Custom Connectors
Bridge between Claude and remote MCP servers, connecting Claude to external tools and data sources.
Data layer
Data Layer Protocol
Example
Expose tools, resources, and prompts
MCP servers can expose tools, resources, and prompts to clients.
Feature States
Features may be marked as Deprecated under the feature lifecycle and deprecation policy.
Filesystem Server
MCP server providing file read, create, move, rename and search tools.
Form mode elicitation
Server asks client to collect structured data using a schema for input form and validation.
Layers
MCP Inspector
Interactive, transport-agnostic testing UI for invoking tools, prompts, and resources.
MCPServer class
Uses Python type hints and docstrings to generate tool definitions.
mcp-server-dev plugin
Reference plugin providing three composing MCP development skills.
Multi Round-Trip Requests (MRTR)
Server responds with InputRequiredResult carrying elicitation/create requests; client retries with inputResponses.
Negotiation
Every request declares its protocol version via the io.modelcontextprotocol/protocolVersion key in its _meta field.
Notifications
notifications/message
Protocol logging mechanism deprecated as of protocol version 2026-07-28.
Participants
Primitives
Prompts
Server primitive providing interaction templates.
Resource Templates
Dynamic URIs with parameters for flexible queries, including title and MIME metadata.
Resources
Server primitive providing context data.
Resources and Prompts
Connected server resources and prompts become available in Claude conversations.
Revisions
Revisions may be marked as Draft, Current, or Final.
RFC 5424 severity levels
Eight severity levels from debug through emergency used for log messages.
Scope
SDK tiering system
SDKs are classified into tiers based on feature completeness, protocol support, and maintenance commitment.
server/discover
Call to see which protocol versions the server supports.
server/discover request
Lets clients query a server's supported protocol versions, capabilities, and identity.
Statelessness and discovery
STDIO server logging
Never write to stdout in STDIO servers; use logging to stderr.
Stdio transport
Transport using standard input/output streams, typically for local servers.
Streamable HTTP transport
Transport typically used by remote servers serving many clients.
Tools
Server primitive enabling AI actions.
Transport layer
URL mode elicitation
Server provides a URL for out-of-band interaction; data never passes through the client.