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SEP-2322: Multi Round-Trip Requests Model Context Protocol · in the page seps/2322-MRTR …upgrade of your horizontally scaled server instances to deploy a new version of a tool implementation. The old version had two input requests with keys "github\_login" and "google\_login". However, i… SEP-2484: Require Conformance Tests for Standards Track SEPs to Reach Final Status Model Context Protocol · in the page seps/2484-conformance-tests-required-for-final-seps …ormance repository, targeting the conformance repository's draft spec-version tag for the upcoming release. 2. **A traceability file** accompanies the scenario. See below. 3. **The scenario passes** a… SEP-2567: Sessionless MCP via Explicit State Handles Model Context Protocol · in the page seps/2567-sessionless-mcp …s. [SEP-2575] removes the `initialize` handshake and carries protocol version and capabilities per-request; this proposal is the complementary change that removes sessions and the `Mcp-Session-Id` hea… SEP-2575: Make MCP Stateless Model Context Protocol · in the page seps/2575-stateless-mcp …s and establishes several key pieces of information: 1. MCP Protocol Version 2. Server Capabilities and `serverInfo` 3. Client Capabilities and `clientInfo` The requirement of this initialization ha… SEP-2577: Deprecate Roots, Sampling, and Logging Model Context Protocol · in the page seps/2577-deprecate-roots-sampling-and-logging …essage`) These features are deprecated starting in the specification version that includes this SEP (expected June 2026). They will continue to be fully functional in all specification versions relea… SEP-2596: Specification Feature Lifecycle and Deprecation Policy Model Context Protocol · in the page seps/2596-spec-feature-lifecycle-and-deprecation …1], large implementers described indefinite support for past protocol versions as "corrosive tech debt." The [Stability over velocity][design-principles] design principle observes that "removing from… SEP-2640: Skills Extension Model Context Protocol · in the page seps/2640-skills-extension …ibution.** A server and the skill that teaches an agent to use it are versioned, discovered, and installed separately. Users installing a server from a registry have no signal that a companion skill e… SEP-2663: Tasks Extension Model Context Protocol · in the page seps/2663-tasks-extension …ding block of MCP and are expected to be supported in future protocol versions. The experimental `tasks` feature in the `2025-11-25` specification served as a stopgap until the protocol's extension me… SEP-3398: Release Cycle Updates Model Context Protocol · in the page seps/3398-release-cycle-updates …. ### SDK Beta — 1.5 Months Before Release Tier 1 SDKs publish beta versions supporting the frozen specification scope 1.5 months before release, giving client and server developers half a month to… SEP-973: Expose additional metadata for Implementations, Resources, Tools and Prompts Model Context Protocol · in the page seps/973-expose-additional-metadata-for-implementations-res …entation */ export interface Implementation extends BaseMetadata { version: string; /** * An optional list of icons for this implementation. * This can be used by clients to display the imp… SEP-986: Specify Format for Tool Names Model Context Protocol · in the page seps/986-specify-format-for-tool-names …ming tool names SHOULD be supported as aliases for at least one major version, with a deprecation warning. * Tool authors SHOULD update their documentation and code to use the new format. * A migratio… SEP-991: Enable URL-based Client Registration using OAuth Client ID Metadata Documents Model Context Protocol · in the page seps/991-enable-url-based-client-registration-using-oauth-c …in the linked RFC, aiming not to repeat most of it. Below is a short version of what we'll need to specify. ```mermaid theme={null} sequenceDiagram participant User participant Client… Lifecycle Model Context Protocol · in the page specification/2024-11-05/basic/lifecycle …nagement. 1. **Initialization**: Capability negotiation and protocol version agreement 2. **Operation**: Normal protocol communication 3. **Shutdown**: Graceful termination of the connection ```merm… Roots Model Context Protocol · in the page specification/2024-11-05/client/roots …cess to. This can be combined with automatic workspace detection from version control systems or project files. However, implementations are free to expose roots through any interface pattern that su… Resources Model Context Protocol · in the page specification/2024-11-05/server/resources …ies) that don’t otherwise have a standard MIME type. ### git:// Git version control integration. ## Error Handling Servers **SHOULD** return standard JSON-RPC errors for common failure cases: * R… Authorization Model Context Protocol · in the page specification/2025-03-26/basic/authorization …covery Headers MCP clients *SHOULD* include the header `MCP-Protocol-Version: <protocol-version>` during Server Metadata Discovery to allow the MCP server to respond based on the MCP protocol version… Lifecycle Model Context Protocol · in the page specification/2025-03-26/basic/lifecycle …nagement. 1. **Initialization**: Capability negotiation and protocol version agreement 2. **Operation**: Normal protocol communication 3. **Shutdown**: Graceful termination of the connection ```merm… Transports Model Context Protocol · in the page specification/2025-03-26/basic/transports …ication/2024-11-05/basic/transports.md#http-with-sse) from > protocol version 2024-11-05. See the [backwards compatibility](#backwards-compatibility) > guide below. In the **Streamable HTTP** transpo… Roots Model Context Protocol · in the page specification/2025-03-26/client/roots …cess to. This can be combined with automatic workspace detection from version control systems or project files. However, implementations are free to expose roots through any interface pattern that su… Resources Model Context Protocol · in the page specification/2025-03-26/server/resources …ies) that don’t otherwise have a standard MIME type. ### git:// Git version control integration. ## Error Handling Servers **SHOULD** return standard JSON-RPC errors for common failure cases: * R… Lifecycle Model Context Protocol · in the page specification/2025-06-18/basic/lifecycle …nagement. 1. **Initialization**: Capability negotiation and protocol version agreement 2. **Operation**: Normal protocol communication 3. **Shutdown**: Graceful termination of the connection ```merm… Transports Model Context Protocol · in the page specification/2025-06-18/basic/transports …ication/2024-11-05/basic/transports.md#http-with-sse) from > protocol version 2024-11-05. See the [backwards compatibility](#backwards-compatibility) > guide below. In the **Streamable HTTP** transpo… Key Changes Model Context Protocol · in the page specification/2025-06-18/changelog …tocol/modelcontextprotocol/pull/603)) 8. Require [negotiated protocol version to be specified](https://modelcontextprotocol.io/specification/2025-06-18/basic/transports.md#protocol-version-header)… Elicitation Model Context Protocol · in the page specification/2025-06-18/client/elicitation # Elicitation > [!NOTE] > > Elicitation is newly introduced in this version of the MCP specification and its design may evolve in future protocol versions. The Model Context Protocol (MCP) provides… Roots Model Context Protocol · in the page specification/2025-06-18/client/roots …cess to. This can be combined with automatic workspace detection from version control systems or project files. However, implementations are free to expose roots through any interface pattern that su… Schema Reference Model Context Protocol · in the page specification/2025-06-18/schema …re-symbol">\{</span><br /> <span class="tsd-kind-property">protocolVersion</span><span class="tsd-signature-symbol">:</span> <span class="tsd-signature-type">string</span><span class="tsd-signature… Resources Model Context Protocol · in the page specification/2025-06-18/server/resources …ies) that don’t otherwise have a standard MIME type. ### git:// Git version control integration. ### Custom URI Schemes Custom URI schemes **MUST** be in accordance with [RFC3986](https://datatrac… Authorization Model Context Protocol · in the page specification/2025-11-25/basic/authorization …ion. This option is included for backwards compatibility with earlier versions of the MCP authorization spec. ## Scope Selection Strategy When implementing authorization flows, MCP clients **SHOULD*… Lifecycle Model Context Protocol · in the page specification/2025-11-25/basic/lifecycle …nagement. 1. **Initialization**: Capability negotiation and protocol version agreement 2. **Operation**: Normal protocol communication 3. **Shutdown**: Graceful termination of the connection ```merm… Transports Model Context Protocol · in the page specification/2025-11-25/basic/transports …ication/2024-11-05/basic/transports.md#http-with-sse) from > protocol version 2024-11-05. See the [backwards compatibility](#backwards-compatibility) > guide below. In the **Streamable HTTP** transpo… Tasks Model Context Protocol · in the page specification/2025-11-25/basic/utilities/tasks # Tasks > [!NOTE] > > Tasks were introduced in version 2025-11-25 of the MCP specification and are currently considered **experimental**. > The design and behavior of tasks may evolve in future proto… Elicitation Model Context Protocol · in the page specification/2025-11-25/client/elicitation …New feature:** URL mode elicitation is introduced in the `2025-11-25` version of the MCP specification. Its design and implementation may change in future protocol revisions. URL mode elicitation ena… Roots Model Context Protocol · in the page specification/2025-11-25/client/roots …cess to. This can be combined with automatic workspace detection from version control systems or project files. However, implementations are free to expose roots through any interface pattern that su… Schema Reference Model Context Protocol · in the page specification/2025-11-25/schema …electEnumSchema instead. This interface will be removed in a future version.</p> </div> <section class="tsd-panel tsd-member"> <div class="tsd-anchor-link" id="legacytitledenumschema-type" data-type… Resources Model Context Protocol · in the page specification/2025-11-25/server/resources …ies) that don’t otherwise have a standard MIME type. ### git:// Git version control integration. ### Custom URI Schemes Custom URI schemes **MUST** be in accordance with [RFC3986](https://datatrac… Architecture Model Context Protocol · in the page specification/2026-07-28/architecture/index …rotocol: every request is self-contained and carries its own protocol version and capabilities. This architecture enables users to integrate AI capabilities across applications while maintaining clear… Client Registration Model Context Protocol · in the page specification/2026-07-28/basic/authorization/client-registration …ion. This option is included for backwards compatibility with earlier versions of the MCP authorization spec. ### Application Type and Redirect URI Constraints When authorization servers support Ope… Authorization Model Context Protocol · in the page specification/2026-07-28/basic/authorization/index …owing implementations to adopt multiple extensions simultaneously * **Versioned independently** - Extensions follow the core MCP versioning cycle but may adopt independent versioning as needed A list… Overview Model Context Protocol · in the page specification/2026-07-28/basic/index …work together: * **Base Protocol**: Core JSON-RPC message types * **Versioning and Compatibility**: Protocol version negotiation, extension negotiation, and interoperability with earlier protocol re… Multi Round-Trip Requests Model Context Protocol · in the page specification/2026-07-28/basic/patterns/mrtr …> [!NOTE] > > Multi Round-Trip Requests (MRTR) was introduced in this version of the MCP > specification. This replaces the previous approach of sending server-initiated > requests. Servers **MUST** s… Subscriptions Model Context Protocol · in the page specification/2026-07-28/basic/patterns/subscriptions …, "params": { "_meta": { "io.modelcontextprotocol/protocolVersion": "2026-07-28", "io.modelcontextprotocol/clientInfo": { "name": "ExampleClient", "version": "1.0.0"… Overview Model Context Protocol · in the page specification/2026-07-28/basic/transports/index …adata travels in the message body: every request carries its protocol version and client capabilities in [`_meta.io.modelcontextprotocol/*`](https://modelcontextprotocol.io/specification/2026-07-28/ba… stdio Model Context Protocol · in the page specification/2026-07-28/basic/transports/stdio …ransport is carried inline in the JSON-RPC message body. The protocol version, per-request capabilities, and optional client identity live in [`_meta.io.modelcontextprotocol/*`][meta-fields]; the meth… Streamable HTTP Model Context Protocol · in the page specification/2026-07-28/basic/transports/streamable-http …amable HTTP > [!NOTE] > > Streamable HTTP was introduced in protocol version 2025-03-26 as a replacement > for the \[HTTP+SSE transport]\[http-sse] from protocol version 2024-11-05. > [!NOTE] > > Re… Key Changes Model Context Protocol · in the page specification/2026-07-28/changelog …ations/initialized` handshake. Every request now carries its protocol version and client capabilities in `_meta` (`io.modelcontextprotocol/protocolVersion`, `io.modelcontextprotocol/clientCapabilities… Elicitation Model Context Protocol · in the page specification/2026-07-28/client/elicitation …New feature:** URL mode elicitation is introduced in the `2025-11-25` version of the MCP specification. Its design and implementation may change in future protocol revisions. URL mode elicitation ena… Roots Model Context Protocol · in the page specification/2026-07-28/client/roots …G] > > **Deprecated**: The Roots feature is deprecated as of protocol version > `2026-07-28` > ([SEP-2577](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/2577)). > Under the [featur… Sampling Model Context Protocol · in the page specification/2026-07-28/client/sampling …> > **Deprecated**: The Sampling feature is deprecated as of protocol version > `2026-07-28` > ([SEP-2577](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/2577)). > Under the [featur… Schema Reference Model Context Protocol · in the page specification/2026-07-28/schema …link" data-typedoc-h="4">Deprecated</div><p>Deprecated as of protocol version 2026-07-28 (SEP-2577). Remains in the specification for at least twelve months; see the deprecated features registry.<… Discovery Model Context Protocol · in the page specification/2026-07-28/server/discover …`server/discover` lets a client query a server's supported protocol versions, capabilities, and identity before sending any other requests. Servers **MUST** implement it. ## Request The request ca…