MCP Documentation Server

[Model Context Protocol home page](https://modelcontextprotocol.io/) Version 2025-06-18 (latest) Search... Ctrl K Search... Navigation Key Changes [Documentation](https://modelcontextprotocol.io/docs/getting-started/intro) [Specification](https://modelcontextprotocol.io/specification/2025-06-18) [Community](https://modelcontextprotocol.io/community/communication) [About MCP](https://modelcontextprotocol.io/about) On this page - [Major changes](https://modelcontextprotocol.io/specification/2025-06-18/changelog#major-changes) - [Other schema changes](https://modelcontextprotocol.io/specification/2025-06-18/changelog#other-schema-changes) - [Full changelog](https://modelcontextprotocol.io/specification/2025-06-18/changelog#full-changelog) This document lists changes made to the Model Context Protocol (MCP) specification since the previous revision, [2025-03-26](https://modelcontextprotocol.io/specification/2025-03-26). <h2>Major changes</h2> 1. Remove support for JSON-RPC **[batching](https://www.jsonrpc.org/specification#batch)** (PR [#416](https://github.com/modelcontextprotocol/specification/pull/416)) 2. Add support for [structured tool output](https://modelcontextprotocol.io/specification/2025-06-18/server/tools#structured-content) (PR [#371](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/371)) 3. Classify MCP servers as [OAuth Resource Servers](https://modelcontextprotocol.io/specification/2025-06-18/basic/authorization#authorization-server-discovery), adding protected resource metadata to discover the corresponding Authorization server. (PR [#338](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/338)) 4. Require MCP clients to implement Resource Indicators as described in [RFC 8707](https://www.rfc-editor.org/rfc/rfc8707.html) to prevent malicious servers from obtaining access tokens. (PR [#734](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/734)) 5. Clarify [security considerations](https://modelcontextprotocol.io/specification/2025-06-18/basic/authorization#security-considerations) and best practices in the authorization spec and in a new [security best practices page](https://modelcontextprotocol.io/specification/2025-06-18/basic/security_best_practices). 6. Add support for **[elicitation](https://modelcontextprotocol.io/specification/2025-06-18/client/elicitation)**, enabling servers to request additional information from users during interactions. (PR [#382](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/382)) 7. Add support for **[resource links](https://modelcontextprotocol.io/specification/2025-06-18/server/tools#resource-links)** in tool call results. (PR [#603](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/603)) 8. Require [negotiated protocol version to be specified](https://modelcontextprotocol.io/specification/2025-06-18/basic/transports#protocol-version-header) via `MCP-Protocol-Version` header in subsequent requests when using HTTP (PR [#548](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/548)). 9. Change **SHOULD** to **MUST** in [Lifecycle Operation](https://modelcontextprotocol.io/specification/2025-06-18/basic/lifecycle#operation) <h2>Other schema changes</h2> 1. Add `_meta` field to additional interface types (PR [#710](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/710)), and specify [proper usage](https://modelcontextprotocol.io/specification/2025-06-18/basic#meta). 2. Add `context` field to `CompletionRequest`, providing for completion requests to include previously-resolved variables (PR [#598](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/598)). 3. Add `title` field for human-friendly display names, so that `name` can be used as a programmatic identifier (PR [#663](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/663)) <h2>Full changelog</h2> For a complete list of all changes that have been made since the last protocol revision, [see GitHub](https://github.com/modelcontextprotocol/specification/compare/2025-03-26...2025-06-18). Was this page helpful? YesNo [Specification](https://modelcontextprotocol.io/specification/2025-06-18) [Architecture](https://modelcontextprotocol.io/specification/2025-06-18/architecture/index) Assistant Responses are generated using AI and may contain mistakes.