Versioning - Model Context Protocol Documentation Index Fetch the complete documentation index at: /llms.txt Use this file to discover all available pages before exploring further. Skip to main content Model Context Protocol home page Version 2026-07-28 (latest) Search... ⌘ K Ask Assistant ⌘ I * Blog * GitHub Search... Navigation About MCP Versioning Documentation Specification Extensions Registry SEPs Community Get started * What is MCP? About MCP * Architecture * Servers * Clients * Versioning Develop with MCP * Connect to local MCP servers * Connect to remote MCP Servers * Build with Agent Skills * Build an MCP server * Clients * SDKs * Security Developer tools * Inspector * Debugging Examples * Example Servers On this page * Revisions * Feature States * Negotiation About MCP Versioning Copy page Copy page Copy page Copy page The Model Context Protocol uses string-based version identifiers following the format YYYY-MM-DD , to indicate the last date backwards incompatible changes were made. The protocol version will not be incremented when the protocol is updated, as long as the changes maintain backwards compatibility. This allows for incremental improvements while preserving interoperability. ​ Revisions Revisions may be marked as: * Draft : in-progress specifications, not yet ready for consumption. * Current : the current protocol version, which is ready for use and may continue to receive backwards compatible changes. * Final : past, complete specifications that will not be changed. The current protocol version is 2026-07-28 . ​ Feature States Individual features of the specification may additionally be marked as Deprecated under the feature lifecycle and deprecation policy : the feature remains part of the specification, but is scheduled for removal. Deprecated features document a migration path (or state that none is required) and remain in the specification for at least twelve months, or at least ninety days under the policy’s expedited-removal exception , before they become eligible for removal, after which they may be Removed in a future revision. Features that are currently Deprecated are listed in the deprecated features registry . ​ Negotiation Every request declares the protocol version it is using via the io.modelcontextprotocol/protocolVersion key in its _meta field, and the server accepts or rejects each request independently. On Streamable HTTP, the same value is also carried in the MCP-Protocol-Version header . Clients and servers MAY support multiple protocol versions simultaneously. If the server does not support the requested version, it responds with an UnsupportedProtocolVersionError listing the versions it does support. The client can then retry the request with a mutually supported version, or surface an error to the user if none exists. Clients that want to select a version up front can call server/discover , a mandatory RPC that returns the server’s supported protocol versions, capabilities, and identity in a single request. Calling it is optional: a client is free to send any request directly and handle a version error if one comes back. For interoperability with servers and clients that implement the handshake-based protocol revisions ( 2025-11-25 and earlier), see Backward Compatibility . Was this page helpful? Yes No Clients Connect to local MCP servers github Assistant Responses are generated using AI and may contain mistakes.