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Architecture Model Context Protocol · in the page specification/2025-11-25/architecture/index …ection-numbers" /> The Model Context Protocol (MCP) follows a client-host-server architecture where each host can run multiple client instances. This architecture enables users to integrate AI capabi… Authorization Model Context Protocol · in the page specification/2025-11-25/basic/authorization …rization server are beyond the scope of this specification. It may be hosted with the resource server or a separate entity. The [Authorization Server Discovery section](#authorization-server-discovery… Overview Model Context Protocol · in the page specification/2025-11-25/basic/index …r local app URI schemes. * Disallow scheme changes and redirects to hosts on different origins. * Be resilient against resource exhaustion attacks stemming from oversized images, large dimensions, o… Transports Model Context Protocol · in the page specification/2025-11-25/basic/transports …no `id` 2. When running locally, servers **SHOULD** bind only to localhost (127.0.0.1) rather than all network interfaces (0.0.0.0) 3. Servers **SHOULD** implement proper authentication for all connec… Tasks Model Context Protocol · in the page specification/2025-11-25/basic/utilities/tasks …Note> When a task is created in response to a `tools/call` request, host applications may wish to return control to the model while the task is executing. This allows the model to continue processin… Elicitation Model Context Protocol · in the page specification/2025-11-25/client/elicitation …es before sending * For URL mode, clearly display the target domain/host and gather user consent before navigation to the target URL </Warning> ## Capabilities Clients that support elicitation **M… Specification Model Context Protocol · in the page specification/2025-11-25/index …w.jsonrpc.org/) 2.0 messages to establish communication between: * **Hosts**: LLM applications that initiate connections * **Clients**: Connectors within the host application * **Servers**: Services… Schema Reference Model Context Protocol · in the page specification/2025-11-25/schema …4 encoding or any tokenization), if known.</p> <p>This can be used by Hosts to display file sizes and estimate context window usage.</p> </div><aside class="tsd-sources"> <p>Inherited from <a href="#r… Resources Model Context Protocol · in the page specification/2025-11-25/server/resources …del Resources in MCP are designed to be **application-driven**, with host applications determining how to incorporate context based on their needs. For example, applications could: * Expose resourc… Logging Model Context Protocol · in the page specification/2025-11-25/server/utilities/logging …a": { "error": "Connection failed", "details": { "host": "localhost", "port": 5432 } } } } ``` ## Message Flow ```mermaid theme={null} sequenceDiagram par… Architecture Model Context Protocol · in the page specification/2026-07-28/architecture/index …ection-numbers" /> The Model Context Protocol (MCP) follows a client-host-server architecture where each host can run multiple client instances. MCP is a stateless protocol: every request is self-con… Authorization Server Discovery Model Context Protocol · in the page specification/2026-07-28/basic/authorization/authorization-server-discovery …of the server's MCP endpoint: `https://example.com/public/mcp` could host metadata at `https://example.com/.well-known/oauth-protected-resource/public/mcp` * At the root: `https://example.com/.wel… Client Registration Model Context Protocol · in the page specification/2026-07-28/basic/authorization/client-registration …. Key requirements include: **For MCP Clients:** * Clients **MUST** host their metadata document at an HTTPS URL following RFC requirements * The `client_id` URL **MUST** use the "https" scheme and… Authorization Model Context Protocol · in the page specification/2026-07-28/basic/authorization/index …rization server are beyond the scope of this specification. It may be hosted with the resource server or a separate entity. [Authorization Server Discovery](/specification/2026-07-28/basic/authorizati… Authorization Security Considerations Model Context Protocol · in the page specification/2026-07-28/basic/authorization/security-considerations …* be served over HTTPS. 2. All redirect URIs **MUST** be either `localhost` or use HTTPS. ## Authorization Code Protection An attacker who has gained access to an authorization code contained in an… Overview Model Context Protocol · in the page specification/2026-07-28/basic/index …*MUST** be disabled by default and **SHOULD** enforce an allowlist of hosts or at minimum reject loopback, link-local, and private network addresses, apply timeouts and size limits, and log dereferenc… Streamable HTTP Model Context Protocol · in the page specification/2026-07-28/basic/transports/streamable-http …o `id`. 2. When running locally, servers **SHOULD** bind only to localhost (127.0.0.1) rather than all network interfaces (0.0.0.0). 3. Servers **SHOULD** implement proper authentication for all co… Elicitation Model Context Protocol · in the page specification/2026-07-28/client/elicitation …es before sending * For URL mode, clearly display the target domain/host and gather user consent before navigation to the target URL </Warning> ## Capabilities Clients that support elicitation **M… Specification Model Context Protocol · in the page specification/2026-07-28/index …w.jsonrpc.org/) 2.0 messages to establish communication between: * **Hosts**: LLM applications that initiate connections * **Clients**: Connectors within the host application * **Servers**: Services… Schema Reference Model Context Protocol · in the page specification/2026-07-28/schema …4 encoding or any tokenization), if known.</p> <p>This can be used by Hosts to display file sizes and estimate context window usage.</p> </div><aside class="tsd-sources"> <p>Inherited from <a href="#r… Resources Model Context Protocol · in the page specification/2026-07-28/server/resources …del Resources in MCP are designed to be **application-driven**, with host applications determining how to incorporate context based on their needs. For example, applications could: * Expose resourc… Logging Model Context Protocol · in the page specification/2026-07-28/server/utilities/logging …a": { "error": "Connection failed", "details": { "host": "localhost", "port": 5432 } } } } ``` ## Error Handling If the `io.modelcontextprotocol/logLevel` val… Architecture Model Context Protocol · in the page specification/draft/architecture/index …ection-numbers" /> The Model Context Protocol (MCP) follows a client-host-server architecture where each host can run multiple client instances. MCP is a stateless protocol: every request is self-con… Authorization Server Discovery Model Context Protocol · in the page specification/draft/basic/authorization/authorization-server-discovery …of the server's MCP endpoint: `https://example.com/public/mcp` could host metadata at `https://example.com/.well-known/oauth-protected-resource/public/mcp` * At the root: `https://example.com/.wel… Client Registration Model Context Protocol · in the page specification/draft/basic/authorization/client-registration …. Key requirements include: **For MCP Clients:** * Clients **MUST** host their metadata document at an HTTPS URL following RFC requirements * The `client_id` URL **MUST** use the "https" scheme and… Authorization Model Context Protocol · in the page specification/draft/basic/authorization/index …rization server are beyond the scope of this specification. It may be hosted with the resource server or a separate entity. [Authorization Server Discovery](/specification/draft/basic/authorization/au… Authorization Security Considerations Model Context Protocol · in the page specification/draft/basic/authorization/security-considerations …* be served over HTTPS. 2. All redirect URIs **MUST** be either `localhost` or use HTTPS. ## Authorization Code Protection An attacker who has gained access to an authorization code contained in an… Overview Model Context Protocol · in the page specification/draft/basic/index …*MUST** be disabled by default and **SHOULD** enforce an allowlist of hosts or at minimum reject loopback, link-local, and private network addresses, apply timeouts and size limits, and log dereferenc… Streamable HTTP Model Context Protocol · in the page specification/draft/basic/transports/streamable-http …o `id`. 2. When running locally, servers **SHOULD** bind only to localhost (127.0.0.1) rather than all network interfaces (0.0.0.0). 3. Servers **SHOULD** implement proper authentication for all co… Elicitation Model Context Protocol · in the page specification/draft/client/elicitation …es before sending * For URL mode, clearly display the target domain/host and gather user consent before navigation to the target URL </Warning> ## Capabilities Clients that support elicitation **M… Specification Model Context Protocol · in the page specification/draft/index …w.jsonrpc.org/) 2.0 messages to establish communication between: * **Hosts**: LLM applications that initiate connections * **Clients**: Connectors within the host application * **Servers**: Services… Schema Reference Model Context Protocol · in the page specification/draft/schema …4 encoding or any tokenization), if known.</p> <p>This can be used by Hosts to display file sizes and estimate context window usage.</p> </div><aside class="tsd-sources"> <p>Inherited from <a href="#r… Resources Model Context Protocol · in the page specification/draft/server/resources …del Resources in MCP are designed to be **application-driven**, with host applications determining how to incorporate context based on their needs. For example, applications could: * Expose resourc… Logging Model Context Protocol · in the page specification/draft/server/utilities/logging …a": { "error": "Connection failed", "details": { "host": "localhost", "port": 5432 } } } } ``` ## Error Handling If the `io.modelcontextprotocol/logLevel` val…