1,120 pages for message.
Titles and paths first, then pages whose text carries it. Each row opens that page as this site last read it.
Sampling
Model Context Protocol · in the page
specification/2025-06-18/client/sampling
…null} { "capabilities": { "sampling": {} } } ``` ## Protocol Messages ### Creating Messages To request a language model generation, servers send a `sampling/createMessage` request: **Reque…
Specification
Model Context Protocol · in the page
specification/2025-06-18/index
…workflows The protocol uses [JSON-RPC](https://www.jsonrpc.org/) 2.0 messages to establish communication between: * **Hosts**: LLM applications that initiate connections * **Clients**: Connectors wi…
Schema Reference
Model Context Protocol · in the page
specification/2025-06-18/schema
…class="tsd-signature-symbol">;</span> <span class="tsd-kind-property">message</span><span class="tsd-signature-symbol">:</span> <span class="tsd-signature-type">string</span><span class="tsd-signature…
Prompts
Model Context Protocol · in the page
specification/2025-06-18/server/prompts
…mpt templates to clients. Prompts allow servers to provide structured messages and instructions for interacting with language models. Clients can discover available prompts, retrieve their contents, a…
Resources
Model Context Protocol · in the page
specification/2025-06-18/server/resources
…Only list change notifications supported } } } ``` ## Protocol Messages ### Listing Resources To discover available resources, clients send a `resources/list` request. This operation supports…
Tools
Model Context Protocol · in the page
specification/2025-06-18/server/tools
…notifications when the list of available tools changes. ## Protocol Messages ### Listing Tools To discover available tools, clients send a `tools/list` request. This operation supports [pagination…
Completion
Model Context Protocol · in the page
specification/2025-06-18/server/utilities/completion
…l} { "capabilities": { "completions": {} } } ``` ## Protocol Messages ### Requesting Completions To get completion suggestions, clients send a `completion/complete` request specifying what…
Logging
Model Context Protocol · in the page
specification/2025-06-18/server/utilities/logging
…(MCP) provides a standardized way for servers to send structured log messages to clients. Clients can control logging verbosity by setting minimum log levels, with servers sending notifications conta…
Architecture
Model Context Protocol · in the page
specification/2025-11-25/architecture/index
…andles protocol negotiation and capability exchange * Routes protocol messages bidirectionally * Manages subscriptions and notifications * Maintains security boundaries between servers A host applica…
Overview
Model Context Protocol · in the page
specification/2025-11-25/basic/index
…ey components that work together: * **Base Protocol**: Core JSON-RPC message types * **Lifecycle Management**: Connection initialization, capability negotiation, and session control * **Authorizati…
Lifecycle
Model Context Protocol · in the page
specification/2025-11-25/basic/lifecycle
…"create": {} }, "sampling": { "createMessage": {} } } } }, "clientInfo": { "name": "ExampleClient", "title": "Example Clien…
Transports
Model Context Protocol · in the page
specification/2025-11-25/basic/transports
# Transports MCP uses JSON-RPC to encode messages. JSON-RPC messages **MUST** be UTF-8 encoded. The protocol currently defines two standard transport mechanisms for client-server communication: 1.…
Cancellation
Model Context Protocol · in the page
specification/2025-11-25/basic/utilities/cancellation
…ts optional cancellation of in-progress requests through notification messages. Either side can send a cancellation notification to indicate that a previously-issued request should be terminated. ##…
Ping
Model Context Protocol · in the page
specification/2025-11-25/basic/utilities/ping
…client or server can initiate a ping by sending a `ping` request. ## Message Format A ping request is a standard JSON-RPC request with no parameters: ```json theme={null} { "jsonrpc": "2.0", "i…
Progress
Model Context Protocol · in the page
specification/2025-11-25/basic/utilities/progress
…al progress tracking for long-running operations through notification messages. Either side can send progress notifications to provide updates about operation status. ## Progress Flow When a party w…
Tasks
Model Context Protocol · in the page
specification/2025-11-25/basic/utilities/tasks
…ports the `tasks/cancel` operation | | `tasks.requests.sampling.createMessage` | Client supports task-augmented `sampling/createMessage` requests | | `tasks.requests.elicitation.create` | Client suppo…
Key Changes
Model Context Protocol · in the page
specification/2025-11-25/changelog
…dio transport may use stderr for all types of logging, not just error messages (PR [#670](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/670)). 2. Add optional `description` field t…
Elicitation
Model Context Protocol · in the page
specification/2025-11-25/client/elicitation
…equests with modes that are not supported by the client. ## Protocol Messages ### Elicitation Requests To request information from a user, servers send an `elicitation/create` request. All elicita…
Roots
Model Context Protocol · in the page
specification/2025-11-25/client/roots
…will emit notifications when the list of roots changes. ## Protocol Messages ### Listing Roots To retrieve roots, servers send a `roots/list` request: **Request:** ```json theme={null} { "json…
Sampling
Model Context Protocol · in the page
specification/2025-11-25/client/sampling
…. These values > may be removed in future spec releases. ## Protocol Messages ### Creating Messages To request a language model generation, servers send a `sampling/createMessage` request: **Reque…
Specification
Model Context Protocol · in the page
specification/2025-11-25/index
…workflows The protocol uses [JSON-RPC](https://www.jsonrpc.org/) 2.0 messages to establish communication between: * **Hosts**: LLM applications that initiate connections * **Clients**: Connectors wi…
Schema Reference
Model Context Protocol · in the page
specification/2025-11-25/schema
…></svg></a></div> </section> </div> <div class="type"> ### `JSONRPCMessage` <div class="tsd-signature"><span class="tsd-kind-type-alias">JSONRPCMessage</span><span class="tsd-signature-symbol">:…
Prompts
Model Context Protocol · in the page
specification/2025-11-25/server/prompts
…mpt templates to clients. Prompts allow servers to provide structured messages and instructions for interacting with language models. Clients can discover available prompts, retrieve their contents, a…
Resources
Model Context Protocol · in the page
specification/2025-11-25/server/resources
…Only list change notifications supported } } } ``` ## Protocol Messages ### Listing Resources To discover available resources, clients send a `resources/list` request. This operation supports…
Tools
Model Context Protocol · in the page
specification/2025-11-25/server/tools
…notifications when the list of available tools changes. ## Protocol Messages ### Listing Tools To discover available tools, clients send a `tools/list` request. This operation supports [pagination…
Completion
Model Context Protocol · in the page
specification/2025-11-25/server/utilities/completion
…l} { "capabilities": { "completions": {} } } ``` ## Protocol Messages ### Requesting Completions To get completion suggestions, clients send a `completion/complete` request specifying what…
Logging
Model Context Protocol · in the page
specification/2025-11-25/server/utilities/logging
…(MCP) provides a standardized way for servers to send structured log messages to clients. Clients can control logging verbosity by setting minimum log levels, with servers sending notifications conta…
Architecture
Model Context Protocol · in the page
specification/2026-07-28/architecture/index
…protocol version and capabilities to every request * Routes protocol messages bidirectionally * Manages subscriptions and notifications * Maintains security boundaries between servers A host applica…
Overview
Model Context Protocol · in the page
specification/2026-07-28/basic/index
…ey components that work together: * **Base Protocol**: Core JSON-RPC message types * **Versioning and Compatibility**: Protocol version negotiation, extension negotiation, and interoperability with e…
Cancellation
Model Context Protocol · in the page
specification/2026-07-28/basic/patterns/cancellation
…ts optional cancellation of in-progress requests through notification messages. A client **SHOULD** send a cancellation notification to indicate that a request it previously issued should be terminate…
Overview
Model Context Protocol · in the page
specification/2026-07-28/basic/patterns/index
# Overview This page defines the message patterns of the core protocol: the ways a client and server compose JSON-RPC [requests, responses, and notifications](/specification/2026-07-28/basic/index.md…
Multi Round-Trip Requests
Model Context Protocol · in the page
specification/2026-07-28/basic/patterns/mrtr
…nd server-to-client requests (such as > `roots/list`, `sampling/createMessage`, or `elicitation/create`) using the > MRTR pattern. The previous pattern of server-initiated requests is no longer > supp…
Progress
Model Context Protocol · in the page
specification/2026-07-28/basic/patterns/progress
…al progress tracking for long-running operations through notification messages. The server **MAY** send progress notifications to report the status of requests the client has issued. ## Progress Flow…
Subscriptions
Model Context Protocol · in the page
specification/2026-07-28/basic/patterns/subscriptions
…**MUST** send `notifications/subscriptions/acknowledged` as the first message carrying the subscription's ID in `_meta` under `io.modelcontextprotocol/subscriptionId`, and **MUST NOT** send any notifi…
Overview
Model Context Protocol · in the page
specification/2026-07-28/basic/transports/index
…verview This page defines what a transport must provide to carry MCP messages, the standard transport bindings, and the requirements for defining new ones. Protocol semantics are identical on every…
stdio
Model Context Protocol · in the page
specification/2026-07-28/basic/transports/stdio
…over the subprocess's standard streams: * The server reads JSON-RPC messages from `stdin` and writes JSON-RPC messages to `stdout`. * Each message is a single JSON-RPC request, notification, or re…
Streamable HTTP
Model Context Protocol · in the page
specification/2026-07-28/basic/transports/streamable-http
…of a [`subscriptions/listen`][subscriptions-listen] request. See [Message Flow](#message-flow) for sequence diagrams of these interactions. The server **MUST** provide a single HTTP endpoint path…
Versioning and Compatibility
Model Context Protocol · in the page
specification/2026-07-28/basic/versioning
…"jsonrpc": "2.0", "id": 1, "error": { "code": -32022, "message": "Unsupported protocol version", "data": { "supported": ["2026-07-28", "2025-11-25"], "requested": "1900-…
Key Changes
Model Context Protocol · in the page
specification/2026-07-28/changelog
…ped notifications such as `notifications/progress` and `notifications/message` continue to flow on the response stream of the request they relate to, not the `subscriptions/listen` stream ([SEP-2575](…
Elicitation
Model Context Protocol · in the page
specification/2026-07-28/client/elicitation
…equests with modes that are not supported by the client. ## Protocol Messages ### Elicitation Requests Servers **MAY** request information from a user during the processing of a client request, by…
Roots
Model Context Protocol · in the page
specification/2026-07-28/client/roots
…clientCapabilities": { "roots": {} } } } ``` ## Protocol Messages ### Listing Roots To retrieve roots during the processing of a client request, servers send an `InputRequiredResult` co…
Sampling
Model Context Protocol · in the page
specification/2026-07-28/client/sampling
…es > registry](/specification/2026-07-28/deprecated.md). ## Protocol Messages ### Creating Messages To request a language model generation during the processing of a client request, servers send an…
Specification
Model Context Protocol · in the page
specification/2026-07-28/index
…workflows The protocol uses [JSON-RPC](https://www.jsonrpc.org/) 2.0 messages to establish communication between: * **Hosts**: LLM applications that initiate connections * **Clients**: Connectors wi…
Schema Reference
Model Context Protocol · in the page
specification/2026-07-28/schema
…></svg></a></div> </section> </div> <div class="type"> ### `JSONRPCMessage` <div class="tsd-signature"><span class="tsd-kind-type-alias">JSONRPCMessage</span><span class="tsd-signature-symbol">:…
Prompts
Model Context Protocol · in the page
specification/2026-07-28/server/prompts
…mpt templates to clients. Prompts allow servers to provide structured messages and instructions for interacting with language models. Clients can discover available prompts, retrieve their contents, a…
Resources
Model Context Protocol · in the page
specification/2026-07-28/server/resources
…credentials are per-request input, not connection state. ## Protocol Messages ### Listing Resources To discover available resources, clients send a `resources/list` request. This operation supports…
Tools
Model Context Protocol · in the page
specification/2026-07-28/server/tools
…ache hit rates when tools are included in model context. ## Protocol Messages ### Listing Tools To discover available tools, clients send a `tools/list` request. This operation supports [pagination…
Completion
Model Context Protocol · in the page
specification/2026-07-28/server/utilities/completion
…l} { "capabilities": { "completions": {} } } ``` ## Protocol Messages ### Requesting Completions To get completion suggestions, clients send a `completion/complete` request specifying what…
Logging
Model Context Protocol · in the page
specification/2026-07-28/server/utilities/logging
…(MCP) provides a standardized way for servers to send structured log messages to clients. Clients control logging verbosity per-request via `_meta`, with servers sending notifications containing seve…
Architecture
Model Context Protocol · in the page
specification/draft/architecture/index
…protocol version and capabilities to every request * Routes protocol messages bidirectionally * Manages subscriptions and notifications * Maintains security boundaries between servers A host applica…