Spec diff: 2025-11-25 → 2026-07-28

This page compares the official schema.json of the two revisions. The tables are generated when the site is built, from copies of both files kept in our repository, so they show exactly what the schema says. The notes on methods are ours.

145 definitions in 2025-11-25, 155 in 2026-07-28: 42 added, 32 removed, 76 changed (16 of them only in wording).

What a schema diff does not show

Some of the biggest changes are rules, not types: HTTP headers such as Mcp-Method, the 400 and 404 status codes, and which features are deprecated. Deprecated features (Roots, Sampling, Logging, HTTP+SSE, Dynamic Client Registration) are still in the schema, so they do not appear as removed here. For those, read the overview of 2026-07-28 and the changelog.

Methods

Thirteen methods are gone from the core protocol and three are new.

Method	Change	What it means
initialize	Removed	There is no handshake: every request carries the protocol version and client capabilities in _meta. spec
logging/setLevel	Removed	The log level is now set per request with io.modelcontextprotocol/logLevel in _meta. Logging itself is deprecated, not removed. spec
notifications/elicitation/complete	Removed	Dropped along with the elicitationId of URL-mode elicitation. The client learns the outcome by retrying the original request. spec
notifications/initialized	Removed	Went away with initialize. spec
notifications/roots/list_changed	Removed	Roots itself is deprecated; a server asks for roots through an input request instead. spec
notifications/subscriptions/acknowledged	Added	First message on a subscriptions/listen stream: the subset of requested notification types the server will actually send. spec
notifications/tasks/status	Removed	Gone from the core protocol with the rest of tasks. Check the io.modelcontextprotocol/tasks extension for what it offers now. spec
ping	Removed	A 2026-07-28 server answers it with -32601 Method not found. spec
resources/subscribe	Removed	List the resource URIs in the resourceSubscriptions filter of subscriptions/listen. spec
resources/unsubscribe	Removed	Close or cancel the subscriptions/listen request instead. spec
server/discover	Added	Returns supported protocol versions, capabilities and server info. Servers must implement it; clients may call it first, and dual-era stdio clients should use it as the probe before falling back to initialize. spec
subscriptions/listen	Added	One long-lived request whose response stream carries the change notifications the client opted in to. Replaces the HTTP GET stream and resources/subscribe. spec
tasks/cancel	Removed	Gone from the core protocol with the rest of tasks. Check the io.modelcontextprotocol/tasks extension for what it offers now. spec
tasks/get	Removed	Moved out of the core protocol into the official extension io.modelcontextprotocol/tasks, which was redesigned. spec
tasks/list	Removed	Gone from the core protocol, and the tasks extension has no tasks/list. spec
tasks/result	Removed	Gone from the core protocol. The tasks extension polls with tasks/get instead of blocking on tasks/result. spec

New definitions

Most of the new types serve three features: the per-request _meta envelope (RequestMetaObject, ResultMetaObject), multi round-trip requests (InputRequiredResult, InputRequests, InputResponses) and caching (CacheableResult). The …ResultResponse types are complete JSON-RPC responses that wrap the matching result, and the error types give each spec error code its own schema.

Definition	Fields
CacheableResult	_meta, cacheScope, resultType, ttlMs
CallToolResultResponse	id, jsonrpc, result
CompleteResultResponse	id, jsonrpc, result
DiscoverRequest server/discover	id, jsonrpc, method, params
DiscoverResult	_meta, cacheScope, capabilities, instructions, resultType, supportedVersions, ttlMs
DiscoverResultResponse	id, jsonrpc, result
GetPromptResultResponse	id, jsonrpc, result
HeaderMismatchError	error, id, jsonrpc
InputRequest
InputRequests
InputRequiredResult	_meta, inputRequests, requestState, resultType
InputResponse
InputResponseRequestParams	_meta, inputResponses, requestState
InputResponses
InternalError	code, data, message
InvalidParamsError	code, data, message
InvalidRequestError	code, data, message
JSONArray
JSONObject
JSONValue
ListPromptsResultResponse	id, jsonrpc, result
ListResourcesResultResponse	id, jsonrpc, result
ListResourceTemplatesResultResponse	id, jsonrpc, result
ListToolsResultResponse	id, jsonrpc, result
MetaObject
MethodNotFoundError	code, data, message
MissingRequiredClientCapabilityError	error, id, jsonrpc
NotificationMetaObject	io.modelcontextprotocol/subscriptionId
ParseError	code, data, message
ReadResourceResultResponse	id, jsonrpc, result
RequestMetaObject	io.modelcontextprotocol/clientCapabilities, io.modelcontextprotocol/clientInfo, io.modelcontextprotocol/logLevel, io.modelcontextprotocol/protocolVersion, progressToken
ResultMetaObject	io.modelcontextprotocol/serverInfo
ResultType
SubscriptionFilter	promptsListChanged, resourceSubscriptions, resourcesListChanged, toolsListChanged
SubscriptionsAcknowledgedNotification notifications/subscriptions/acknowledged	jsonrpc, method, params
SubscriptionsAcknowledgedNotificationParams	_meta, notifications
SubscriptionsListenRequest subscriptions/listen	id, jsonrpc, method, params
SubscriptionsListenRequestParams	_meta, notifications
SubscriptionsListenResult	_meta, resultType
SubscriptionsListenResultMetaObject	io.modelcontextprotocol/serverInfo, io.modelcontextprotocol/subscriptionId
SubscriptionsListenResultResponse	id, jsonrpc, result
UnsupportedProtocolVersionError	error, id, jsonrpc

Removed definitions

Definition	Method
CancelTaskRequest	tasks/cancel
CancelTaskResult
CreateTaskResult
ElicitationCompleteNotification	notifications/elicitation/complete
GetTaskPayloadRequest	tasks/result
GetTaskPayloadResult
GetTaskRequest	tasks/get
GetTaskResult
InitializedNotification	notifications/initialized
InitializeRequest	initialize
InitializeRequestParams
InitializeResult
ListTasksRequest	tasks/list
ListTasksResult
PingRequest	ping
RelatedTaskMetadata
RootsListChangedNotification	notifications/roots/list_changed
ServerRequest
SetLevelRequest	logging/setLevel
SetLevelRequestParams
SubscribeRequest	resources/subscribe
SubscribeRequestParams
Task
TaskAugmentedRequestParams
TaskMetadata
TaskStatus
TaskStatusNotification	notifications/tasks/status
TaskStatusNotificationParams
ToolExecution
UnsubscribeRequest	resources/unsubscribe
UnsubscribeRequestParams
URLElicitationRequiredError

Changed definitions

+ is a field that was added, − one that was removed and ~ one whose type or constraints changed. The arrow shows the old and new shape. Two patterns repeat across many rows: results gained a required resultType, and list results gained ttlMs and cacheScope.

Definition	Fields
AudioContent	~ _meta (object → MetaObject)
BlobResourceContents	~ _meta (object → MetaObject)
CallToolRequestParams	~ _meta (object → RequestMetaObject; removed: progressToken) + inputResponses (InputResponses) + requestState (string) − task (TaskMetadata) required + _meta
CallToolResult	~ _meta (object → ResultMetaObject) + resultType (string) ~ structuredContent (object → any JSON) required + resultType
CancelledNotificationParams	~ _meta (object → NotificationMetaObject) required + requestId
ClientCapabilities	~ elicitation (constraints changed) ~ experimental (constraints changed) + extensions (object) ~ roots (removed: listChanged) ~ sampling (constraints changed) − tasks (object)
ClientNotification	+ jsonrpc ("2.0") + method ("notifications/cancelled") + params (CancelledNotificationParams) required + jsonrpc, method, params
ClientRequest
ClientResult
CompleteRequestParams	~ _meta (object → RequestMetaObject; removed: progressToken) required + _meta
CompleteResult	~ _meta (object → ResultMetaObject) ~ completion (constraints changed) + resultType (string) required + resultType
CreateMessageRequest	− id (RequestId) − jsonrpc ("2.0") required − id, jsonrpc
CreateMessageRequestParams	− _meta (object) ~ metadata (object → JSONObject) − task (TaskMetadata)
CreateMessageResult	~ _meta (object → MetaObject)
ElicitRequest	− id (RequestId) − jsonrpc ("2.0") required − id, jsonrpc
ElicitRequestFormParams	− _meta (object) − task (TaskMetadata)
ElicitRequestParams
ElicitRequestURLParams	− _meta (object) − elicitationId (string) − task (TaskMetadata) required − elicitationId
ElicitResult	− _meta (object)
EmbeddedResource	~ _meta (object → MetaObject)
GetPromptRequestParams	~ _meta (object → RequestMetaObject; removed: progressToken) + inputResponses (InputResponses) + requestState (string) required + _meta
GetPromptResult	~ _meta (object → ResultMetaObject) + resultType (string) required + resultType
ImageContent	~ _meta (object → MetaObject)
ListPromptsRequest	required + params
ListPromptsResult	~ _meta (object → ResultMetaObject) + cacheScope ("private" | "public") + resultType (string) + ttlMs (integer) required + cacheScope, resultType, ttlMs
ListResourcesRequest	required + params
ListResourcesResult	~ _meta (object → ResultMetaObject) + cacheScope ("private" | "public") + resultType (string) + ttlMs (integer) required + cacheScope, resultType, ttlMs
ListResourceTemplatesRequest	required + params
ListResourceTemplatesResult	~ _meta (object → ResultMetaObject) + cacheScope ("private" | "public") + resultType (string) + ttlMs (integer) required + cacheScope, resultType, ttlMs
ListRootsRequest	− id (RequestId) − jsonrpc ("2.0") ~ params (RequestParams → object; added: _meta) required − id, jsonrpc
ListRootsResult	− _meta (object)
ListToolsRequest	required + params
ListToolsResult	~ _meta (object → ResultMetaObject) + cacheScope ("private" | "public") + resultType (string) + ttlMs (integer) required + cacheScope, resultType, ttlMs
LoggingMessageNotificationParams	~ _meta (object → NotificationMetaObject)
NotificationParams	~ _meta (object → NotificationMetaObject)
PaginatedRequest	required + params
PaginatedRequestParams	~ _meta (object → RequestMetaObject; removed: progressToken) required + _meta
PaginatedResult	~ _meta (object → ResultMetaObject) + resultType (string) required + resultType
ProgressNotificationParams	~ _meta (object → NotificationMetaObject)
Prompt	~ _meta (object → MetaObject)
ReadResourceRequestParams	~ _meta (object → RequestMetaObject; removed: progressToken) + inputResponses (InputResponses) + requestState (string) required + _meta
ReadResourceResult	~ _meta (object → ResultMetaObject) + cacheScope ("private" | "public") + resultType (string) + ttlMs (integer) required + cacheScope, resultType, ttlMs
RequestParams	~ _meta (object → RequestMetaObject; removed: progressToken) required + _meta
Resource	~ _meta (object → MetaObject)
ResourceContents	~ _meta (object → MetaObject)
ResourceLink	~ _meta (object → MetaObject)
ResourceRequestParams	~ _meta (object → RequestMetaObject; removed: progressToken) required + _meta
ResourceTemplate	~ _meta (object → MetaObject)
ResourceUpdatedNotificationParams	~ _meta (object → NotificationMetaObject)
Result	~ _meta (object → ResultMetaObject) + resultType (string) required + resultType
Root	~ _meta (object → MetaObject)
SamplingMessage	~ _meta (object → MetaObject)
ServerCapabilities	~ completions (object → JSONObject) ~ experimental (constraints changed) + extensions (object) ~ logging (object → JSONObject) − tasks (object)
ServerNotification
ServerResult
TextContent	~ _meta (object → MetaObject)
TextResourceContents	~ _meta (object → MetaObject)
Tool	~ _meta (object → MetaObject) − execution (ToolExecution) ~ inputSchema (removed: properties, required) ~ outputSchema (removed: properties, required, type)
ToolResultContent	~ _meta (object → MetaObject) ~ structuredContent (object → any JSON)
ToolUseContent	~ _meta (object → MetaObject)

16 more definitions changed only in their descriptions

BaseMetadata, CancelledNotification, EmptyResult, Icon, Implementation, LegacyTitledEnumSchema, LoggingMessageNotification, PromptArgument, PromptListChangedNotification, PromptMessage, PromptReference, ResourceListChangedNotification, ResourceUpdatedNotification, ToolAnnotations, ToolChoice, ToolListChangedNotification

How this page is built

• The two schema files are copied unmodified from the specification repository at commit 9850cae, with their SHA-256 hashes recorded next to them. A check fails the build if a file changes without its hash being updated.
• The diff ignores description and title text when deciding whether a definition changed structurally. Definitions that differ only in wording are listed separately.
• Links go to the official schema reference. A few base types have no anchor there; those link to the top of the page.

Related

• MCP 2026-07-28 in plain language
• Migrate from 2025-11-25 to 2026-07-28