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Protocol types of the targeted revision. Protocol types for MCP specification revision 2026-07-28.

Generated from the official schema.json and schema.ts (commit 271ecc9accafdd9b83a3c869fa67c22953b2af80).

Modules§

error_codes: JSON-RPC error codes defined by the schema.
methods: Method names defined by the schema.

Structs§

Annotations: Optional annotations for the client. The client can use annotations to inform how objects are used or displayed
AudioContent: Audio provided to or from an LLM.
BaseMetadata: Base interface for metadata with name (identifier) and title (display name) properties.
BlobResourceContents
BooleanSchema
CacheableResult: A result that supports a time-to-live (TTL) hint for client-side caching.
CallToolRequest: Used by the client to invoke a tool provided by the server.
CallToolRequestParams: Parameters for a tools/call request.
CallToolResult: The result returned by the server for a CallToolRequesttools/call request.
CallToolResultResponse: A successful response from the server for a CallToolRequesttools/call request.
CancelledNotification: This notification is sent by the client to indicate that it is cancelling a request it previously issued.
CancelledNotificationParams: Parameters for a notifications/cancelled notification.
ClientCapabilities: Capabilities a client may support. Known capabilities are defined here, in this schema, but this is not a closed set: any client can define its own, additional capabilities.
ClientCapabilitiesElicitation: Present if the client supports elicitation from the server.
ClientCapabilitiesRoots: Present if the client supports listing roots.
ClientCapabilitiesSampling: Present if the client supports sampling from an LLM.
ClientNotification: This notification is sent by the client to indicate that it is cancelling a request it previously issued.
CompleteRequest: A request from the client to the server, to ask for completion options.
CompleteRequestParams: Parameters for a completion/complete request.
CompleteRequestParamsArgument: The argument’s information
CompleteRequestParamsContext: Additional, optional context for completions
CompleteResult: The result returned by the server for a CompleteRequestcompletion/complete request.
CompleteResultCompletion
CompleteResultResponse: A successful response from the server for a CompleteRequestcompletion/complete request.
CreateMessageRequestDeprecated: A request from the server to sample an LLM via the client. The client has full discretion over which model to select. The client should also inform the user before beginning sampling, to allow them to inspect the request (human in the loop) and decide whether to approve it.
CreateMessageRequestParamsDeprecated: Parameters for a sampling/createMessage request.
CreateMessageResultDeprecated: The result returned by the client for a CreateMessageRequestsampling/createMessage request. The client should inform the user before returning the sampled message, to allow them to inspect the response (human in the loop) and decide whether to allow the server to see it.
DiscoverRequest: A request from the client asking the server to advertise its supported protocol versions, capabilities, and other metadata. Servers MUST implement server/discover. Clients MAY call it but are not required to — version negotiation can also happen inline via per-request _meta.
DiscoverResult: The result returned by the server for a DiscoverRequestserver/discover request.
DiscoverResultResponse: A successful response from the server for a DiscoverRequestserver/discover request.
ElicitRequest: A request from the server to elicit additional information from the user via the client.
ElicitRequestFormParams: The parameters for a request to elicit non-sensitive information from the user via a form in the client.
ElicitRequestFormParamsRequestedSchema: A restricted subset of JSON Schema. Only top-level properties are allowed, without nesting.
ElicitRequestUrlParams: The parameters for a request to elicit information from the user via a URL in the client.
ElicitResult: The result returned by the client for an ElicitRequestelicitation/create request.
EmbeddedResource: The contents of a resource, embedded into a prompt or tool call result.
Error
GetPromptRequest: Used by the client to get a prompt provided by the server.
GetPromptRequestParams: Parameters for a prompts/get request.
GetPromptResult: The result returned by the server for a GetPromptRequestprompts/get request.
GetPromptResultResponse: A successful response from the server for a GetPromptRequestprompts/get request.
HeaderMismatchError: Returned when a server rejects a request because the values in the HTTP headers do not match the corresponding values in the request body, or because required headers are missing or malformed. For HTTP, the response status code MUST be 400 Bad Request.
HeaderMismatchErrorObject
Icon: An optionally-sized icon that can be displayed in a user interface.
Icons: Base interface to add icons property.
ImageContent: An image provided to or from an LLM.
Implementation: Describes the MCP implementation.
InputRequiredResult: An InputRequiredResult sent by the server to indicate that additional input is needed before the request can be completed.
InputResponseRequestParams
InternalError: A JSON-RPC error indicating that an internal error occurred on the receiver. This error is returned when the receiver encounters an unexpected condition that prevents it from fulfilling the request.
InvalidParamsError: A JSON-RPC error indicating that the method parameters are invalid or malformed.
InvalidRequestError: A JSON-RPC error indicating that the request is not a valid request object. This error is returned when the message structure does not conform to the JSON-RPC 2.0 specification requirements for a request (e.g., missing required fields like jsonrpc or method, or using invalid types for these fields).
JsonRpcErrorResponse: A response to a request that indicates an error occurred.
JsonRpcNotification: A notification which does not expect a response.
JsonRpcRequest: A request that expects a response.
JsonRpcResultResponse: A successful (non-error) response to a request.
LegacyTitledEnumSchema: Use TitledSingleSelectEnumSchema instead. This interface will be removed in a future version.
ListPromptsRequest: Sent from the client to request a list of prompts and prompt templates the server has.
ListPromptsResult: The result returned by the server for a ListPromptsRequestprompts/list request.
ListPromptsResultResponse: A successful response from the server for a ListPromptsRequestprompts/list request.
ListResourceTemplatesRequest: Sent from the client to request a list of resource templates the server has.
ListResourceTemplatesResult: The result returned by the server for a ListResourceTemplatesRequestresources/templates/list request.
ListResourceTemplatesResultResponse: A successful response from the server for a ListResourceTemplatesRequestresources/templates/list request.
ListResourcesRequest: Sent from the client to request a list of resources the server has.
ListResourcesResult: The result returned by the server for a ListResourcesRequestresources/list request.
ListResourcesResultResponse: A successful response from the server for a ListResourcesRequestresources/list request.
ListRootsRequestDeprecated: Sent from the server to request a list of root URIs from the client. Roots allow servers to ask for specific directories or files to operate on. A common example for roots is providing a set of repositories or directories a server should operate on.
ListRootsRequestParams
ListRootsResultDeprecated: The result returned by the client for a ListRootsRequestroots/list request. This result contains an array of Root objects, each representing a root directory or file that the server can operate on.
ListToolsRequest: Sent from the client to request a list of tools the server has.
ListToolsResult: The result returned by the server for a ListToolsRequesttools/list request.
ListToolsResultResponse: A successful response from the server for a ListToolsRequesttools/list request.
LoggingMessageNotificationDeprecated: JSONRPCNotification of a log message passed from server to client. The client opts in by setting "io.modelcontextprotocol/logLevel" in a request’s _meta.
LoggingMessageNotificationParamsDeprecated: Parameters for a notifications/message notification.
MethodNotFoundError: A JSON-RPC error indicating that the requested method does not exist or is not available.
MissingRequiredClientCapabilityError: Returned when processing a request requires a capability the client did not declare in clientCapabilities. For HTTP, the response status code MUST be 400 Bad Request.
MissingRequiredClientCapabilityErrorData
MissingRequiredClientCapabilityErrorObject
ModelHintDeprecated: Hints to use for model selection.
ModelPreferencesDeprecated: The server’s preferences for model selection, requested of the client during sampling.
Notification
NotificationMetaObject: Extends MetaObject with additional notification-specific fields. All key naming rules from MetaObject apply.
NotificationParams: Common params for any notification.
NumberSchema
PaginatedRequest
PaginatedRequestParams: Common params for paginated requests.
PaginatedResult
ParseError: A JSON-RPC error indicating that invalid JSON was received by the server. This error is returned when the server cannot parse the JSON text of a message.
ProgressNotification: An out-of-band notification used to inform the receiver of a progress update for a long-running request.
ProgressNotificationParams: Parameters for a ProgressNotificationnotifications/progress notification.
Prompt: A prompt or prompt template that the server offers.
PromptArgument: Describes an argument that a prompt can accept.
PromptListChangedNotification: An optional notification from the server to the client, informing it that the list of prompts it offers has changed. This is only delivered on a SubscriptionsListenRequestsubscriptions/listen stream when the client requested it via the promptsListChanged filter field.
PromptMessage: Describes a message returned as part of a prompt.
PromptReference: Identifies a prompt.
ReadResourceRequest: Sent from the client to the server, to read a specific resource URI.
ReadResourceRequestParams: Parameters for a resources/read request.
ReadResourceResult: The result returned by the server for a ReadResourceRequestresources/read request.
ReadResourceResultResponse: A successful response from the server for a ReadResourceRequestresources/read request.
Request
RequestMetaObject: Extends MetaObject with additional request-specific fields. All key naming rules from MetaObject apply.
RequestParams: Common params for any request.
Resource: A known resource that the server is capable of reading.
ResourceContents: The contents of a specific resource or sub-resource.
ResourceLink: A resource that the server is capable of reading, included in a prompt or tool call result.
ResourceListChangedNotification: An optional notification from the server to the client, informing it that the list of resources it can read from has changed. This is only delivered on a SubscriptionsListenRequestsubscriptions/listen stream when the client requested it via the resourcesListChanged filter field.
ResourceRequestParams: Common params for resource-related requests.
ResourceTemplate: A template description for resources available on the server.
ResourceTemplateReference: A reference to a resource or resource template definition.
ResourceUpdatedNotification: A notification from the server to the client, informing it that a resource has changed and may need to be read again. This is only sent for resources the client opted in to via the resourceSubscriptions field of a SubscriptionsListenRequestsubscriptions/listen request.
ResourceUpdatedNotificationParams: Parameters for a notifications/resources/updated notification.
Result: Common result fields.
ResultMetaObject: Extends MetaObject with additional result-specific fields. All key naming rules from MetaObject apply.
RootDeprecated: Represents a root directory or file that the server can operate on.
SamplingMessageDeprecated: Describes a message issued to or received from an LLM API.
ServerCapabilities: Capabilities that a server may support. Known capabilities are defined here, in this schema, but this is not a closed set: any server can define its own, additional capabilities.
ServerCapabilitiesPrompts: Present if the server offers any prompt templates.
ServerCapabilitiesResources: Present if the server offers any resources to read.
ServerCapabilitiesTools: Present if the server offers any tools to call.
StringSchema
SubscriptionFilter: The set of notification types a client may opt in to on a SubscriptionsListenRequestsubscriptions/listen request.
SubscriptionsAcknowledgedNotification: Sent by the server to acknowledge that a SubscriptionsListenRequestsubscriptions/listen subscription has been established and to report which notification types it agreed to honor.
SubscriptionsAcknowledgedNotificationParams: Parameters for a SubscriptionsAcknowledgedNotificationnotifications/subscriptions/acknowledged notification.
SubscriptionsListenRequest: Sent from the client to open a long-lived channel for receiving notifications outside the context of a specific request. Replaces the previous HTTP GET endpoint and ensures consistent behavior between HTTP and STDIO.
SubscriptionsListenRequestParams: Parameters for a SubscriptionsListenRequestsubscriptions/listen request.
SubscriptionsListenResult: The response to a SubscriptionsListenRequestsubscriptions/listen request, signalling that the subscription has ended gracefully (for example, during server shutdown). Because the listen stream is long-lived, this result is sent only when the server tears the subscription down; an abrupt transport close carries no response. The result body is otherwise empty.
SubscriptionsListenResultMetaObject: Extends ResultMetaObject with the subscription-stream identifier carried by a SubscriptionsListenResult. All key naming rules from MetaObject apply.
SubscriptionsListenResultResponse: A successful response from the server for a SubscriptionsListenRequestsubscriptions/listen request, sent when the server tears the subscription down gracefully.
TextContent: Text provided to or from an LLM.
TextResourceContents
TitledMultiSelectEnumSchema: Schema for multiple-selection enumeration with display titles for each option.
TitledMultiSelectEnumSchemaItems: Schema for array items with enum options and display labels.
TitledMultiSelectEnumSchemaItemsAnyOfItem
TitledSingleSelectEnumSchema: Schema for single-selection enumeration with display titles for each option.
TitledSingleSelectEnumSchemaOneOfItem
Tool: Definition for a tool the client can call.
ToolAnnotations: Additional properties describing a Tool to clients.
ToolChoiceDeprecated: Controls tool selection behavior for sampling requests.
ToolInputSchema: A JSON Schema object defining the expected parameters for the tool.
ToolListChangedNotification: An optional notification from the server to the client, informing it that the list of tools it offers has changed. This is only delivered on a SubscriptionsListenRequestsubscriptions/listen stream when the client requested it via the toolsListChanged filter field.
ToolOutputSchema: An optional JSON Schema object defining the structure of the tool’s output returned in the structuredContent field of a CallToolResult. This can be any valid JSON Schema 2020-12.
ToolResultContentDeprecated: The result of a tool use, provided by the user back to the assistant.
ToolUseContentDeprecated: A request from the assistant to call a tool.
UnsupportedProtocolVersionError: Returned when the request’s protocol version is unknown to the server or unsupported (e.g., a known experimental or draft version the server has chosen not to implement). For HTTP, the response status code MUST be 400 Bad Request.
UnsupportedProtocolVersionErrorData
UnsupportedProtocolVersionErrorObject
UntitledMultiSelectEnumSchema: Schema for multiple-selection enumeration without display titles for options.
UntitledMultiSelectEnumSchemaItems: Schema for the array items.
UntitledSingleSelectEnumSchema: Schema for single-selection enumeration without display titles for options.

Enums§

ArrayType: The constant "array".
AudioType: The constant "audio".
BooleanType: The constant "boolean".
CacheScope: Indicates the intended scope of the cached response, analogous to HTTP Cache-Control: public vs Cache-Control: private.
CallToolResultResponseResult
ClientRequest
CompleteRequestParamsRef
CompletionCompleteMethod: The constant "completion/complete".
ContentBlock
CreateMessageRequestParamsIncludeContext: A request to include context from one or more MCP servers (including the caller), to be attached to the prompt. The client MAY ignore this request.
CreateMessageResultContent
ElicitRequestParams: The parameters for a request to elicit additional information from the user via the client.
ElicitResultAction: The user action in response to the elicitation.
ElicitResultContentValue
ElicitResultContentValueScalar
ElicitationCreateMethod: The constant "elicitation/create".
EmbeddedResourceResource
EnumSchema
FormMode: The constant "form".
GetPromptResultResponseResult
IconTheme: Optional specifier for the theme this icon is designed for. "light" indicates the icon is designed to be used with a light background, and "dark" indicates the icon is designed to be used with a dark background.
ImageType: The constant "image".
InputRequest
InputResponse
JsonRpcMessage: Refers to any valid JSON-RPC object that can be decoded off the wire, or encoded to be sent.
JsonRpcResponse: A response to a request, containing either the result or error.
JsonRpcVersion: The constant "2.0".
LoggingLevelDeprecated: The severity of a log message.
MultiSelectEnumSchema
NotificationsCancelledMethod: The constant "notifications/cancelled".
NotificationsMessageMethod: The constant "notifications/message".
NotificationsProgressMethod: The constant "notifications/progress".
NotificationsPromptsListChangedMethod: The constant "notifications/prompts/list_changed".
NotificationsResourcesListChangedMethod: The constant "notifications/resources/list_changed".
NotificationsResourcesUpdatedMethod: The constant "notifications/resources/updated".
NotificationsSubscriptionsAcknowledgedMethod: The constant "notifications/subscriptions/acknowledged".
NotificationsToolsListChangedMethod: The constant "notifications/tools/list_changed".
NumberSchemaType
ObjectType: The constant "object".
PrimitiveSchemaDefinition: Restricted schema definitions that only allow primitive types without nested objects or arrays.
ProgressToken: A progress token, used to associate progress notifications with the original request.
PromptsGetMethod: The constant "prompts/get".
PromptsListMethod: The constant "prompts/list".
ReadResourceResultContentsItem
ReadResourceResultResponseResult
RefPromptType: The constant "ref/prompt".
RefResourceType: The constant "ref/resource".
RequestId: A uniquely identifying ID for a request in JSON-RPC.
ResourceLinkType: The constant "resource_link".
ResourceType: The constant "resource".
ResourcesListMethod: The constant "resources/list".
ResourcesReadMethod: The constant "resources/read".
ResourcesTemplatesListMethod: The constant "resources/templates/list".
Role: The sender or recipient of messages and data in a conversation.
RootsListMethod: The constant "roots/list".
SamplingCreateMessageMethod: The constant "sampling/createMessage".
SamplingMessageContent
SamplingMessageContentBlockDeprecated
ServerDiscoverMethod: The constant "server/discover".
ServerNotification
SingleSelectEnumSchema
StringSchemaFormat
StringType: The constant "string".
SubscriptionsListenMethod: The constant "subscriptions/listen".
TextType: The constant "text".
ToolChoiceMode: Controls the tool use ability of the model:
ToolResultType: The constant "tool_result".
ToolUseType: The constant "tool_use".
ToolsCallMethod: The constant "tools/call".
ToolsListMethod: The constant "tools/list".
UrlMode: The constant "url".

Constants§

PROTOCOL_VERSION: The protocol revision these types describe.

Type Aliases§

Cursor: An opaque token used to represent a cursor for pagination.
EmptyResult: Common result fields.
InputRequests: A map of server-initiated requests that the client must fulfill. Keys are server-assigned identifiers; values are the request objects.
InputResponses: A map of client responses to server-initiated requests. Keys correspond to the keys in the InputRequests map; values are the client’s result for each request.
MetaObject: Represents the contents of a _meta field, which clients and servers use to attach additional metadata to their interactions.
ResultType: Indicates the type of a Result object, allowing the client to determine how to parse the response.

Module spec

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Structs§

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Type Aliases§

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