189 pages for compatibility.

Authorization Model Context Protocol · in the page specification/2025-11-25/basic/authorization …h 2.0 Authorization Server Metadata discovery and [RFC8414 Section 5 "Compatibility Notes"](https://datatracker.ietf.org/doc/html/rfc8414#section-5) for OpenID Connect Discovery 1.0 interoperability.… Overview Model Context Protocol · in the page specification/2025-11-25/basic/index …he following MIME types: * `image/png` - PNG images (safe, universal compatibility) * `image/jpeg` (and `image/jpg`) - JPEG images (safe, universal compatibility) Clients that support rendering icon… Lifecycle Model Context Protocol · in the page specification/2025-11-25/basic/lifecycle …ring this phase, the client and server: * Establish protocol version compatibility * Exchange and negotiate capabilities * Share implementation details The client **MUST** initiate this phase by sen… Transports Model Context Protocol · in the page specification/2025-11-25/basic/transports …http-with-sse) from > protocol version 2024-11-05. See the [backwards compatibility](#backwards-compatibility) > guide below. In the **Streamable HTTP** transport, the server operates as an independe… Elicitation Model Context Protocol · in the page specification/2025-11-25/client/elicitation …": { "form": {}, "url": {} } } } ``` For backwards compatibility, an empty capabilities object is equivalent to declaring support for `form` mode only: ```jsonc theme={null} { "c… Sampling Model Context Protocol · in the page specification/2025-11-25/client/sampling …, audio) in the same message is not allowed. This constraint ensures compatibility with provider APIs that use dedicated roles for tool results (e.g., OpenAI's "tool" role, Gemini's "function" role).… Schema Reference Model Context Protocol · in the page specification/2025-11-25/schema …es:</p> <ul> <li><code>image/png</code> - PNG images (safe, universal compatibility)</li> <li><code>image/jpeg</code> (and <code>image/jpg</code>) - JPEG images (safe, universal compatibility)</li> </… Tools Model Context Protocol · in the page specification/2025-11-25/server/tools …N object in the `structuredContent` field of a result. For backwards compatibility, a tool that returns structured content SHOULD also return the serialized JSON in a TextContent block. > [!NOTE] >… Architecture Model Context Protocol · in the page specification/2026-07-28/architecture/index …dently * Protocol designed for future extensibility * Backwards compatibility is maintained ## Capability Negotiation The Model Context Protocol uses a capability-based negotiation system wher… Authorization Server Discovery Model Context Protocol · in the page specification/2026-07-28/basic/authorization/authorization-server-discovery …2.0 Authorization Server Metadata discovery and [RFC 8414 Section 5 "Compatibility Notes"](https://datatracker.ietf.org/doc/html/rfc8414#section-5) for OpenID Connect Discovery 1.0 interoperability.… Client Registration Model Context Protocol · in the page specification/2026-07-28/basic/authorization/client-registration …c Client Registration](#dynamic-client-registration)**: For backwards compatibility or specific requirements Clients supporting all options **SHOULD** use the following priority order: 1. Use pre-re… Authorization Model Context Protocol · in the page specification/2026-07-28/basic/authorization/index …amic-client-registration) is deprecated and retained for backwards compatibility with authorization servers that do not support Client ID Metadata Documents. 4. MCP servers **MUST** implement OAut… Authorization Security Considerations Model Context Protocol · in the page specification/2026-07-28/basic/authorization/security-considerations …de `code_challenge_methods_supported` in their metadata to ensure MCP compatibility. ## Mix-Up Attacks An attacker that controls one of the authorization servers an MCP client interacts with may att… Overview Model Context Protocol · in the page specification/2026-07-28/basic/index …* **Base Protocol**: Core JSON-RPC message types * **Versioning and Compatibility**: Protocol version negotiation, extension negotiation, and interoperability with earlier protocol revisions * **Mes… Overview Model Context Protocol · in the page specification/2026-07-28/basic/transports/index …rocess-lifecycle rules are specific to standard streams. ## Backward Compatibility Earlier protocol revisions established a connection-scoped session with an `initialize` handshake and allowed serve… stdio Model Context Protocol · in the page specification/2026-07-28/basic/transports/stdio …learn.microsoft.com/windows/win32/procthread/job-objects ## Backward Compatibility A client that supports both modern (per-request-metadata) MCP versions and a legacy version that requires an `initi… Streamable HTTP Model Context Protocol · in the page specification/2026-07-28/basic/transports/streamable-http …avior of Streamable HTTP. Clients must > ensure they handle backwards compatibility correctly. Changes included: > > * Removal of the GET stream endpoint. > * Removal of protocol-level sessions. > > S… Key Changes Model Context Protocol · in the page specification/2026-07-28/changelog …other request for up-front version selection, or use it as a backward-compatibility probe on STDIO ([SEP-2575](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/2575)). 4. Replace the… Elicitation Model Context Protocol · in the page specification/2026-07-28/client/elicitation …"form": {}, "url": {} } } } } ``` For backwards compatibility, an empty capabilities object is equivalent to declaring support for `form` mode only: ```jsonc theme={null} { "_… Sampling Model Context Protocol · in the page specification/2026-07-28/client/sampling …, audio) in the same message is not allowed. This constraint ensures compatibility with provider APIs that use dedicated roles for tool results (e.g., OpenAI's "tool" role, Gemini's "function" role).… Schema Reference Model Context Protocol · in the page specification/2026-07-28/schema …menting this protocol version MUST include this field. For backward compatibility, when a client receives a result from a server implementing an earlier protocol version (which does not include <c… Discovery Model Context Protocol · in the page specification/2026-07-28/server/discover …t`, `prompts/list`, and `resources/list` requests. * **stdio backward-compatibility probe.** On stdio, there is no per-request HTTP status code to drive fallback. A client that supports both modern… Resources Model Context Protocol · in the page specification/2026-07-28/server/resources …ervers **SHOULD** return `-32603` for internal errors. For backwards compatibility, clients **SHOULD** also accept `-32002` as a resource not found error, as earlier protocol versions used this code.… Tools Model Context Protocol · in the page specification/2026-07-28/server/tools …nforms to the tool's `outputSchema` if one is defined. For backwards compatibility, a tool that returns structured content SHOULD also return the serialized JSON in a TextContent block. > [!NOTE] >… Architecture Model Context Protocol · in the page specification/draft/architecture/index …dently * Protocol designed for future extensibility * Backwards compatibility is maintained ## Capability Negotiation The Model Context Protocol uses a capability-based negotiation system wher… Authorization Server Discovery Model Context Protocol · in the page specification/draft/basic/authorization/authorization-server-discovery …2.0 Authorization Server Metadata discovery and [RFC 8414 Section 5 "Compatibility Notes"](https://datatracker.ietf.org/doc/html/rfc8414#section-5) for OpenID Connect Discovery 1.0 interoperability.… Client Registration Model Context Protocol · in the page specification/draft/basic/authorization/client-registration …c Client Registration](#dynamic-client-registration)**: For backwards compatibility or specific requirements Clients supporting all options **SHOULD** use the following priority order: 1. Use pre-re… Authorization Model Context Protocol · in the page specification/draft/basic/authorization/index …amic-client-registration) is deprecated and retained for backwards compatibility with authorization servers that do not support Client ID Metadata Documents. 4. MCP servers **MUST** implement OAut… Authorization Security Considerations Model Context Protocol · in the page specification/draft/basic/authorization/security-considerations …de `code_challenge_methods_supported` in their metadata to ensure MCP compatibility. ## Mix-Up Attacks An attacker that controls one of the authorization servers an MCP client interacts with may att… Overview Model Context Protocol · in the page specification/draft/basic/index …* **Base Protocol**: Core JSON-RPC message types * **Versioning and Compatibility**: Protocol version negotiation, extension negotiation, and interoperability with earlier protocol revisions * **Mes… Overview Model Context Protocol · in the page specification/draft/basic/transports/index …rocess-lifecycle rules are specific to standard streams. ## Backward Compatibility Earlier protocol revisions established a connection-scoped session with an `initialize` handshake and allowed serve… stdio Model Context Protocol · in the page specification/draft/basic/transports/stdio …learn.microsoft.com/windows/win32/procthread/job-objects ## Backward Compatibility A client that supports both modern (per-request-metadata) MCP versions and a legacy version that requires an `initi… Streamable HTTP Model Context Protocol · in the page specification/draft/basic/transports/streamable-http …avior of Streamable HTTP. Clients must > ensure they handle backwards compatibility correctly. Changes included: > > * Removal of the GET stream endpoint. > * Removal of protocol-level sessions. > > S… Elicitation Model Context Protocol · in the page specification/draft/client/elicitation …"form": {}, "url": {} } } } } ``` For backwards compatibility, an empty capabilities object is equivalent to declaring support for `form` mode only: ```jsonc theme={null} { "_… Sampling Model Context Protocol · in the page specification/draft/client/sampling …, audio) in the same message is not allowed. This constraint ensures compatibility with provider APIs that use dedicated roles for tool results (e.g., OpenAI's "tool" role, Gemini's "function" role).… Schema Reference Model Context Protocol · in the page specification/draft/schema …menting this protocol version MUST include this field. For backward compatibility, when a client receives a result from a server implementing an earlier protocol version (which does not include <c… Discovery Model Context Protocol · in the page specification/draft/server/discover …t`, `prompts/list`, and `resources/list` requests. * **stdio backward-compatibility probe.** On stdio, there is no per-request HTTP status code to drive fallback. A client that supports both modern… Resources Model Context Protocol · in the page specification/draft/server/resources …ervers **SHOULD** return `-32603` for internal errors. For backwards compatibility, clients **SHOULD** also accept `-32002` as a resource not found error, as earlier protocol versions used this code.… Tools Model Context Protocol · in the page specification/draft/server/tools …nforms to the tool's `outputSchema` if one is defined. For backwards compatibility, a tool that returns structured content SHOULD also return the serialized JSON in a TextContent block. > [!NOTE] >…