Model Context Protocol Specification (2025-06-18)
by Model Context Protocol / Anthropic
The authoritative, versioned MCP protocol spec.
Overview
This is the canonical Model Context Protocol specification for the 2025-06-18 revision, published on modelcontextprotocol.io and derived from the protocol's TypeScript schema. It defines MCP's JSON-RPC 2.0 message format, stateful connections, and capability negotiation between Hosts (LLM applications that initiate connections), Clients (connectors inside the host), and Servers (services that provide context and capabilities). It formally specifies the server-offered features (Resources, Prompts, Tools) and client-offered features (Sampling, Roots, Elicitation), plus utilities like progress tracking, cancellation, error reporting, and logging, and lays out the security and trust principles (user consent, data privacy, tool safety, sampling controls) that all implementors MUST address.
At a Glance
- Topic
- MCP
- Level
- Advanced
- Format
- Documentation
- Cost
- Free
- Provider
- Model Context Protocol / Anthropic
- Hands-on
- No
- Certificate
- None
What You’ll Learn
- ✓How MCP's JSON-RPC 2.0 base protocol, stateful sessions, and capability negotiation work
- ✓The server primitives: Resources, Prompts, and Tools
- ✓The client primitives: Sampling, Roots, and Elicitation
- ✓MCP's security and trust model and implementor obligations
- ✓Protocol utilities: progress, cancellation, error reporting, and logging
Highlights
- •The single source of truth for the protocol, tied to the official schema
- •Explicit MUST/SHOULD normative requirements for interoperability
- •Dedicated security and trust & safety principles section
Who It’s For
Best For
- ✓Engineers building MCP clients or servers to spec
- ✓Contributors and tool authors needing exact protocol semantics
Prerequisites
- •Familiarity with JSON-RPC and client-server architectures
- •Comfort reading formal protocol specifications
FAQ
What is Model Context Protocol Specification (2025-06-18)?
The official specification that defines the authoritative requirements of the Model Context Protocol, based on its TypeScript schema. For engineers implementing MCP hosts, clients, or servers who need the ground-truth protocol semantics.
Is Model Context Protocol Specification (2025-06-18) free?
Model Context Protocol Specification (2025-06-18) is free to access.
What level is Model Context Protocol Specification (2025-06-18) for?
Model Context Protocol Specification (2025-06-18) is aimed at a advanced audience. Recommended background: Familiarity with JSON-RPC and client-server architectures, Comfort reading formal protocol specifications.
What will I learn from Model Context Protocol Specification (2025-06-18)?
You'll learn: How MCP's JSON-RPC 2.0 base protocol, stateful sessions, and capability negotiation work; The server primitives: Resources, Prompts, and Tools; The client primitives: Sampling, Roots, and Elicitation; MCP's security and trust model and implementor obligations; Protocol utilities: progress, cancellation, error reporting, and logging.