355 pages for origin.

SEP-1686: Tasks Model Context Protocol · in the page seps/1686-tasks …relies on prompt engineering to steer an agent to poll at all. In the original `long_running_tool` case, the client had no way of knowing if a response would ever be received, while in the `start_long… SEP-2106: Tools `inputSchema` & `outputSchema` Conform to JSON Schema 2020-12 Model Context Protocol · in the page seps/2106-json-schema-2020-12 …| **Author(s)** | John McBride ([@jpmcb](https://github.com/jpmcb)) — original proposal; Ola Hungerford ([@olaservo](https://github.com/olaservo)) — current shepherd, post-SEP-1850 conversion | | **Sp… SEP-2127: MCP Server Cards - HTTP Server Discovery Model Context Protocol · in the page seps/2127-mcp-server-cards …rd list operations. * **CORS**: Wide-open CORS (`Access-Control-Allow-Origin: *`) is acceptable because cards carry only public, read-only metadata. * **Transport security and MITM**: Cards SHOULD be… SEP-2133: Extensions Model Context Protocol · in the page seps/2133-extensions …ty to grant the rights in this agreement 2. Your contribution is your original work, or you have sufficient rights to submit it 3. You grant to Linux Foundation and recipients of the specification a p… SEP-2207: OIDC-Flavored Refresh Token Guidance Model Context Protocol · in the page seps/2207-oidc-refresh-token-guidance …ervers support the `offline_access` scope. The `offline_access` scope originated in OIDC but can be adopted by any OAuth 2.1 Authorization Server as a mechanism to let clients explicitly request refre… SEP-2243: HTTP Header Standardization for Streamable HTTP Transport Model Context Protocol · in the page seps/2243-http-standardization …(i.e., starts with `=?base64?` and ends with `?=`). **Examples**: | Original Value | Reason | Encoded Header Value | | - | - | - | | `"us-west1"` | Plain ASCII | `Mcp-Param-Region: us-west1` | | `"H… SEP-2260: Require Server requests to be associated with a Client request. Model Context Protocol · in the page seps/2260-Require-Server-requests-to-be-associated-with-Client-requests …ge`, and `elicitation/create` requests **MUST** be associated with an originating client-to-server request (e.g., during `tools/call`, `resources/read`, or `prompts/get` processing). Standalone server… SEP-2322: Multi Round-Trip Requests Model Context Protocol · in the page seps/2322-MRTR …can match up the elicitation response on one server instance with the original ongoing tool call on a different server instance. There are two main approaches that can be used to solve this problem t… SEP-2468: Recommend Issuer (iss) Parameter in MCP Auth Responses Model Context Protocol · in the page seps/2468-recommend-issuer-claim-for-auth …server identity, MCP clients can reliably detect and reject responses originating from an unexpected issuer, improving protocol robustness in multi‑identity provider (IdP) environments. This SEP follo… SEP-2567: Sessionless MCP via Explicit State Handles Model Context Protocol · in the page seps/2567-sessionless-mcp …ound-trip, the server has to correlate the eventual response with the original in-flight tool call — state that today lives implicitly in the session. [SEP-2322] (Multi Round-Trip Requests) resolves t… SEP-2575: Make MCP Stateless Model Context Protocol · in the page seps/2575-stateless-mcp …tResources`). The client satisfies the input requests and retries the original request. #### Request Cancellation How a client cancels an in-flight request depends on the transport: * **HTTP.** Clo… SEP-2640: Skills Extension Model Context Protocol · in the page seps/2640-skills-extension …han silently discarding or preferring one. When skills from different origins collide on `name`, hosts MUST resolve the name within a per-origin namespace, identifying servers by a host-assigned label… SEP-2663: Tasks Extension Model Context Protocol · in the page seps/2663-tasks-extension …result of the task. * The structure matches the result type of the original request. * For example, a CallToolRequest task would return the CallToolResult structure. */ result: JSONObject;… Transports Model Context Protocol · in the page specification/2024-11-05/basic/transports …lementing HTTP with SSE transport: 1. Servers **MUST** validate the `Origin` header on all incoming connections to prevent DNS rebinding attacks 2. When running locally, servers **SHOULD** bind only… Progress Model Context Protocol · in the page specification/2024-11-05/basic/utilities/progress …receiver **MAY** then send progress notifications containing: * The original progress token * The current progress value so far * An optional "total" value ```json theme={null} { "jsonrpc": "2.0"… Authorization Model Context Protocol · in the page specification/2025-03-26/basic/authorization …access token bound to the third-party session 7. MCP server completes original OAuth flow with MCP client ```mermaid theme={null} sequenceDiagram participant B as User-Agent (Browser) partici… Transports Model Context Protocol · in the page specification/2025-03-26/basic/transports …menting Streamable HTTP transport: 1. Servers **MUST** validate the `Origin` header on all incoming connections to prevent DNS rebinding attacks 2. When running locally, servers **SHOULD** bind only… Progress Model Context Protocol · in the page specification/2025-03-26/basic/utilities/progress …receiver **MAY** then send progress notifications containing: * The original progress token * The current progress value so far * An optional "total" value * An optional "message" value ```json the… Authorization Model Context Protocol · in the page specification/2025-06-18/basic/authorization …ts to create a secret verifier-challenge pair, ensuring that only the original requestor can exchange an authorization code for tokens. ### Open Redirection An attacker may craft malicious redirect… Transports Model Context Protocol · in the page specification/2025-06-18/basic/transports …menting Streamable HTTP transport: 1. Servers **MUST** validate the `Origin` header on all incoming connections to prevent DNS rebinding attacks 2. When running locally, servers **SHOULD** bind only… Progress Model Context Protocol · in the page specification/2025-06-18/basic/utilities/progress …receiver **MAY** then send progress notifications containing: * The original progress token * The current progress value so far * An optional "total" value * An optional "message" value ```json the… Schema Reference Model Context Protocol · in the page specification/2025-06-18/schema …p>A progress token, used to associate progress notifications with the original request.</p> </div> </div> <div class="type"> ### `RequestId` <div class="tsd-signature"><span class="tsd-kind-type… Authorization Model Context Protocol · in the page specification/2025-11-25/basic/authorization …ate (re-)authorization** with the determined scope set 4. **Retry the original request** with the new authorization no more than a few times and treat this as a permanent authorization failure Client… Overview Model Context Protocol · in the page specification/2025-11-25/basic/index …emes. * Disallow scheme changes and redirects to hosts on different origins. * Be resilient against resource exhaustion attacks stemming from oversized images, large dimensions, or excessive frames… Transports Model Context Protocol · in the page specification/2025-11-25/basic/transports …menting Streamable HTTP transport: 1. Servers **MUST** validate the `Origin` header on all incoming connections to prevent DNS rebinding attacks * If the `Origin` header is present and invalid, se… Progress Model Context Protocol · in the page specification/2025-11-25/basic/utilities/progress …receiver **MAY** then send progress notifications containing: * The original progress token * The current progress value so far * An optional "total" value * An optional "message" value ```json the… Tasks Model Context Protocol · in the page specification/2025-11-25/basic/utilities/tasks …onse, which contains only task data. The result structure matches the original request type (e.g., `CallToolResult` for `tools/call`). To retrieve the result of a completed task, requestors can send… Key Changes Model Context Protocol · in the page specification/2025-11-25/changelog …Clarify that servers must respond with HTTP 403 Forbidden for invalid Origin headers in Streamable HTTP transport. (PR [#1439](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/1439))… Elicitation Model Context Protocol · in the page specification/2025-11-25/client/elicitation …on request. * **MUST** include the `elicitationId` established in the original `elicitation/create` request. Clients: * **MUST** ignore notifications referencing unknown or already-completed IDs. *… Schema Reference Model Context Protocol · in the page specification/2025-11-25/schema …p>A progress token, used to associate progress notifications with the original request.</p> </div> </div> <div class="type"> ### `RequestId` <div class="tsd-signature"><span class="tsd-kind-type… Architecture Model Context Protocol · in the page specification/2026-07-28/architecture/index …Host-->>Client: AI response Client->>Server: Original request (with input) end Server-->>Client: Response Client-->>Host: Update UI or respond to model… Authorization Model Context Protocol · in the page specification/2026-07-28/basic/authorization/index …ate (re-)authorization** with the determined scope set 4. **Retry the original request** with the new authorization no more than a few times and treat this as a permanent authorization failure Client… Authorization Security Considerations Model Context Protocol · in the page specification/2026-07-28/basic/authorization/security-considerations …ts to create a secret verifier-challenge pair, ensuring that only the original requestor can exchange an authorization code for tokens. MCP clients **MUST** use the `S256` code challenge method when… Overview Model Context Protocol · in the page specification/2026-07-28/basic/index …lcontextprotocol/subscriptionId` | Correlates a notification with its originating subscription | [Subscriptions](/specification/2026-07-28/basic/patterns/subscriptions) | | `traceparent`, `tracestate`… Overview Model Context Protocol · in the page specification/2026-07-28/basic/patterns/index …utRequiredResult (inputRequests) Client->>Server: request (id: 2, original params + inputResponses) Server-->>Client: response ``` ## Subscribe and Notify To receive change notifications (li… Multi Round-Trip Requests Model Context Protocol · in the page specification/2026-07-28/basic/patterns/mrtr …equested information from the user or other sources, then retries the original request including the additional requested information. 4. Server determines it has sufficient information to complete th… Progress Model Context Protocol · in the page specification/2026-07-28/basic/patterns/progress …he server **MAY** then send progress notifications containing: * The original progress token * The current progress value so far * An optional "total" value * An optional "message" value ```json the… Subscriptions Model Context Protocol · in the page specification/2026-07-28/basic/patterns/subscriptions …clients **MUST** use this field to correlate notifications with their originating subscription. ```json theme={null} { "jsonrpc": "2.0", "method": "notifications/resources/updated", "params": {… Streamable HTTP Model Context Protocol · in the page specification/2026-07-28/basic/transports/streamable-http …menting Streamable HTTP transport: 1. Servers **MUST** validate the `Origin` header on all incoming connections to prevent DNS rebinding attacks. * If the `Origin` header is present and invalid… Versioning and Compatibility Model Context Protocol · in the page specification/2026-07-28/basic/versioning …** cache the result for the lifetime of the server process (stdio) or origin (HTTP), and **MAY** persist it across restarts of the same server configuration, re-probing if the cached assumption later… Key Changes Model Context Protocol · in the page specification/2026-07-28/changelog …the request. Clients respond with `inputResponses` on a retry of the original request providing the requested information. ([SEP-2322](https://github.com/modelcontextprotocol/modelcontextprotocol/pul… Elicitation Model Context Protocol · in the page specification/2026-07-28/client/elicitation …is not directly informed of the outcome. When the client retries the original request, the server determines from the echoed `requestState` (or its own stored state) whether the out-of-band interacti… Schema Reference Model Context Protocol · in the page specification/2026-07-28/schema …n</a> stream, so the client can correlate the notification with the originating subscription. The key is absent on notifications not delivered via a subscription stream (e.g. progress notificati… Architecture Model Context Protocol · in the page specification/draft/architecture/index …Host-->>Client: AI response Client->>Server: Original request (with input) end Server-->>Client: Response Client-->>Host: Update UI or respond to model… Authorization Model Context Protocol · in the page specification/draft/basic/authorization/index …ate (re-)authorization** with the determined scope set 4. **Retry the original request** with the new authorization no more than a few times and treat this as a permanent authorization failure Client… Authorization Security Considerations Model Context Protocol · in the page specification/draft/basic/authorization/security-considerations …ts to create a secret verifier-challenge pair, ensuring that only the original requestor can exchange an authorization code for tokens. MCP clients **MUST** use the `S256` code challenge method when… Overview Model Context Protocol · in the page specification/draft/basic/index …lcontextprotocol/subscriptionId` | Correlates a notification with its originating subscription | [Subscriptions](/specification/draft/basic/patterns/subscriptions) | | `traceparent`, `tracestate`, `ba… Overview Model Context Protocol · in the page specification/draft/basic/patterns/index …utRequiredResult (inputRequests) Client->>Server: request (id: 2, original params + inputResponses) Server-->>Client: response ``` ## Subscribe and Notify To receive change notifications (li… Multi Round-Trip Requests Model Context Protocol · in the page specification/draft/basic/patterns/mrtr …equested information from the user or other sources, then retries the original request including the additional requested information. 4. Server determines it has sufficient information to complete th… Progress Model Context Protocol · in the page specification/draft/basic/patterns/progress …he server **MAY** then send progress notifications containing: * The original progress token * The current progress value so far * An optional "total" value * An optional "message" value ```json the…