490 pages for metadata.

Authorization Security Considerations Model Context Protocol · in the page specification/2026-07-28/basic/authorization/security-considerations …cover PKCE support, MCP clients **MUST** rely on authorization server metadata to verify this capability: * **OAuth 2.0 Authorization Server Metadata**: If `code_challenge_methods_supported` is absen… Overview Model Context Protocol · in the page specification/2026-07-28/basic/index …es, protocol version, client identity). Every request supplies this metadata in its [`_meta`](#_meta) field. * Servers **SHOULD** be prepared to handle requests associated with multiple tasks, thr… Multi Round-Trip Requests Model Context Protocol · in the page specification/2026-07-28/basic/patterns/mrtr …brevity, the request examples on this page omit the `_meta` request > metadata (`io.modelcontextprotocol/protocolVersion`, > `io.modelcontextprotocol/clientInfo`, and > `io.modelcontextprotocol/client… Progress Model Context Protocol · in the page specification/2026-07-28/basic/patterns/progress …s updates for a request, it includes a `progressToken` in the request metadata. * Progress tokens **MUST** be a string or integer value * Progress tokens can be chosen by the client using any means,… Subscriptions Model Context Protocol · in the page specification/2026-07-28/basic/patterns/subscriptions …thod-specific data beyond the standard result fields and subscription metadata. This is the JSON-RPC response to the long-lived request, correlated by its `id`, and signals that the subscription ended… Overview Model Context Protocol · in the page specification/2026-07-28/basic/transports/index …ding**: it defines how messages are framed and delivered, how request metadata is carried, and how cancellation and termination are signaled. It does not define what the messages mean: the [message pa… stdio Model Context Protocol · in the page specification/2026-07-28/basic/transports/stdio …ification/2026-07-28/schema.md#subscriptionslistenrequest ## Request Metadata All request metadata for the stdio transport is carried inline in the JSON-RPC message body. The protocol version, per-r… Streamable HTTP Model Context Protocol · in the page specification/2026-07-28/basic/transports/streamable-http …supported content types. 3. The client **MUST** include the [request metadata headers](#request-metadata) on each POST request. 4. The body of the HTTP POST **MUST** be a single JSON-RPC *request*… Versioning and Compatibility Model Context Protocol · in the page specification/2026-07-28/basic/versioning …ions that convey version, identity, and capabilities as per-request metadata (revision `2026-07-28` and later). * **Legacy**: protocol versions that establish a session with an `initialize` handsh… Key Changes Model Context Protocol · in the page specification/2026-07-28/changelog …591)) as a client registration mechanism in favor of [Client ID Metadata Documents](/specification/2026-07-28/basic/authorization/client-registration.md#client-id-metadata-documents) ([PR #28… Elicitation Model Context Protocol · in the page specification/2026-07-28/client/elicitation …ients: 1. **MUST NOT** automatically pre-fetch the URL or any of its metadata. 2. **MUST NOT** open the URL without explicit consent from the user. 3. **MUST** show the full URL to the user for exami… Sampling Model Context Protocol · in the page specification/2026-07-28/client/sampling …uired. * `stopSequences`: Array of sequences that stop generation. * `metadata`: Additional provider-specific parameters. The client **MUST** respect the `maxTokens` parameter. The client **MAY** mo… Deprecated Features Model Context Protocol · in the page specification/2026-07-28/deprecated …tprotocol/modelcontextprotocol/pull/2858) | `2026-07-28` | [Client ID Metadata Documents](/specification/2026-07-28/basic/authorization/client-registration.md#client-id-metadata-documents) | First rev… Schema Reference Model Context Protocol · in the page specification/2026-07-28/schema …meta</code> field, which clients and servers use to attach additional metadata to their interactions.</p> <p>Certain key names are reserved by MCP for protocol-level metadata; implementations MUST NOT… Prompts Model Context Protocol · in the page specification/2026-07-28/server/prompts …brevity, the request examples on this page omit the `_meta` request > metadata (`io.modelcontextprotocol/protocolVersion`, > `io.modelcontextprotocol/clientInfo`, and > `io.modelcontextprotocol/client… Resources Model Context Protocol · in the page specification/2026-07-28/server/resources …brevity, the request examples on this page omit the `_meta` request > metadata (`io.modelcontextprotocol/protocolVersion`, > `io.modelcontextprotocol/clientInfo`, and > `io.modelcontextprotocol/client… Tools Model Context Protocol · in the page specification/2026-07-28/server/tools …computations. Each tool is uniquely identified by a name and includes metadata describing its schema. > [!NOTE] > > For brevity, the request examples on this page omit the `_meta` request > metadata… Completion Model Context Protocol · in the page specification/2026-07-28/server/utilities/completion …brevity, the request examples on this page omit the `_meta` request > metadata (`io.modelcontextprotocol/protocolVersion`, > `io.modelcontextprotocol/clientInfo`, and > `io.modelcontextprotocol/client… Pagination Model Context Protocol · in the page specification/2026-07-28/server/utilities/pagination …brevity, the request examples on this page omit the `_meta` request > metadata (`io.modelcontextprotocol/protocolVersion`, > `io.modelcontextprotocol/clientInfo`, and > `io.modelcontextprotocol/client… Authorization Server Discovery Model Context Protocol · in the page specification/draft/basic/authorization/authorization-server-discovery …tion MCP servers **MUST** implement the OAuth 2.0 Protected Resource Metadata ([RFC9728](https://datatracker.ietf.org/doc/html/rfc9728)) specification to indicate the locations of authorization serve… Client Registration Model Context Protocol · in the page specification/draft/basic/authorization/client-registration …gistration mechanisms. Choose based on your scenario: * **[Client ID Metadata Documents](#client-id-metadata-documents)**: When client and server have no prior relationship (most common) * **[Pre-reg… Authorization Model Context Protocol · in the page specification/draft/basic/authorization/index …atracker.ietf.org/doc/html/rfc6750)) * OAuth 2.0 Authorization Server Metadata ([RFC8414](https://datatracker.ietf.org/doc/html/rfc8414)) * OAuth 2.0 Dynamic Client Registration Protocol ([RFC7591… Authorization Security Considerations Model Context Protocol · in the page specification/draft/basic/authorization/security-considerations …cover PKCE support, MCP clients **MUST** rely on authorization server metadata to verify this capability: * **OAuth 2.0 Authorization Server Metadata**: If `code_challenge_methods_supported` is absen… Overview Model Context Protocol · in the page specification/draft/basic/index …es, protocol version, client identity). Every request supplies this metadata in its [`_meta`](#_meta) field. * Servers **SHOULD** be prepared to handle requests associated with multiple tasks, thr… Multi Round-Trip Requests Model Context Protocol · in the page specification/draft/basic/patterns/mrtr …brevity, the request examples on this page omit the `_meta` request > metadata (`io.modelcontextprotocol/protocolVersion`, > `io.modelcontextprotocol/clientInfo`, and > `io.modelcontextprotocol/client… Progress Model Context Protocol · in the page specification/draft/basic/patterns/progress …s updates for a request, it includes a `progressToken` in the request metadata. * Progress tokens **MUST** be a string or integer value * Progress tokens can be chosen by the client using any means,… Subscriptions Model Context Protocol · in the page specification/draft/basic/patterns/subscriptions …thod-specific data beyond the standard result fields and subscription metadata. This is the JSON-RPC response to the long-lived request, correlated by its `id`, and signals that the subscription ended… Overview Model Context Protocol · in the page specification/draft/basic/transports/index …ding**: it defines how messages are framed and delivered, how request metadata is carried, and how cancellation and termination are signaled. It does not define what the messages mean: the [message pa… stdio Model Context Protocol · in the page specification/draft/basic/transports/stdio …/specification/draft/schema.md#subscriptionslistenrequest ## Request Metadata All request metadata for the stdio transport is carried inline in the JSON-RPC message body. The protocol version, per-r… Streamable HTTP Model Context Protocol · in the page specification/draft/basic/transports/streamable-http …supported content types. 3. The client **MUST** include the [request metadata headers](#request-metadata) on each POST request. 4. The body of the HTTP POST **MUST** be a single JSON-RPC *request*… Versioning and Compatibility Model Context Protocol · in the page specification/draft/basic/versioning …ions that convey version, identity, and capabilities as per-request metadata (revision `2026-07-28` and later). * **Legacy**: protocol versions that establish a session with an `initialize` handsh… Elicitation Model Context Protocol · in the page specification/draft/client/elicitation …ients: 1. **MUST NOT** automatically pre-fetch the URL or any of its metadata. 2. **MUST NOT** open the URL without explicit consent from the user. 3. **MUST** show the full URL to the user for exami… Sampling Model Context Protocol · in the page specification/draft/client/sampling …uired. * `stopSequences`: Array of sequences that stop generation. * `metadata`: Additional provider-specific parameters. The client **MUST** respect the `maxTokens` parameter. The client **MAY** mo… Deprecated Features Model Context Protocol · in the page specification/draft/deprecated …tprotocol/modelcontextprotocol/pull/2858) | `2026-07-28` | [Client ID Metadata Documents](/specification/draft/basic/authorization/client-registration.md#client-id-metadata-documents) | First revision… Schema Reference Model Context Protocol · in the page specification/draft/schema …meta</code> field, which clients and servers use to attach additional metadata to their interactions.</p> <p>Certain key names are reserved by MCP for protocol-level metadata; implementations MUST NOT… Prompts Model Context Protocol · in the page specification/draft/server/prompts …brevity, the request examples on this page omit the `_meta` request > metadata (`io.modelcontextprotocol/protocolVersion`, > `io.modelcontextprotocol/clientInfo`, and > `io.modelcontextprotocol/client… Resources Model Context Protocol · in the page specification/draft/server/resources …brevity, the request examples on this page omit the `_meta` request > metadata (`io.modelcontextprotocol/protocolVersion`, > `io.modelcontextprotocol/clientInfo`, and > `io.modelcontextprotocol/client… Tools Model Context Protocol · in the page specification/draft/server/tools …computations. Each tool is uniquely identified by a name and includes metadata describing its schema. > [!NOTE] > > For brevity, the request examples on this page omit the `_meta` request > metadata… Completion Model Context Protocol · in the page specification/draft/server/utilities/completion …brevity, the request examples on this page omit the `_meta` request > metadata (`io.modelcontextprotocol/protocolVersion`, > `io.modelcontextprotocol/clientInfo`, and > `io.modelcontextprotocol/client… Pagination Model Context Protocol · in the page specification/draft/server/utilities/pagination …brevity, the request examples on this page omit the `_meta` request > metadata (`io.modelcontextprotocol/protocolVersion`, > `io.modelcontextprotocol/clientInfo`, and > `io.modelcontextprotocol/client…