Module model 

Basic data types in MCP specification

Structs

Annotations

Optional annotations for the client. The client can use annotations to inform how objects are used or displayed.

ArgumentInfo

ArrayTypeConst

AudioContent

Audio content with base64-encoded data (spec AudioContent).

BooleanSchema

Schema definition for boolean properties.

BooleanTypeConst

CallToolRequestMethod

CallToolRequestParams

Parameters for calling a tool provided by an MCP server.

CallToolResult

The result of a tool call operation.

CancelTaskMethod

CancelTaskParams

CancelledNotificationMethod

CancelledNotificationParam

ClientCapabilities

Builder

ClientCapabilitiesBuilder

ClientCapabilitiesBuilderState

CompleteRequestMethod

CompleteRequestParams

CompleteResult

CompletionContext

Context for completion requests providing previously resolved arguments.

CompletionInfo

ConstTitle

Schema definition for enum properties.

CreateMessageRequestMethod

CreateMessageRequestParamsDeprecated

Parameters for creating a message through LLM sampling.

CreateMessageResultDeprecated

Result of sampling/createMessage (SEP-1577). The result of a sampling/createMessage request containing the generated response.

CreateTaskResult

Result returned in lieu of a standard result to indicate the request will be processed asynchronously (spec CreateTaskResult, resultType: "task").

CustomNotification

A catch-all notification either side can use to send custom messages to its peer.

CustomRequest

A catch-all request either side can use to send custom messages to its peer.

CustomResult

A catch-all response either side can use for custom requests.

DetailedTask

A task with its status-specific payload inlined (spec DetailedTask).

DiscoverRequestMethod

DiscoverRequestParams

Parameters for DiscoverRequest.

DiscoverResult

The server’s response to a DiscoverRequest.

ElicitResult

The result returned by a client in response to an elicitation request.

ElicitationCapability

Elicitation allows servers to request interactive input from users during tool execution. This capability indicates that a client can handle elicitation requests and present appropriate UI to users for collecting the requested information.

ElicitationCreateRequestMethod

ElicitationResponseNotificationMethod

ElicitationSchema

Type-safe elicitation schema for requesting structured user input.

ElicitationSchemaBuilder

Fluent builder for constructing elicitation schemas.

EmbeddedResource

Embedded resource content (spec EmbeddedResource).

EmptyObject

This is commonly used for representing empty objects in MCP messages.

EnumSchemaBuilder

Builder for EnumSchema Allows to create various enum schema types (single/multi select, titled/untitled) with validation of provided parameters

EnumTypeConst

ErrorCode

Standard JSON-RPC error codes used throughout the MCP protocol.

ErrorData

Error information for JSON-RPC error responses.

Extensions

A type map of protocol extensions.

FormElicitationCapability

Capability for handling elicitation requests from servers. Elicitation allows servers to request interactive input from users during tool execution. This capability indicates that a client can handle elicitation requests and present appropriate UI to users for collecting the requested information.

GetPromptRequestMethod

GetPromptRequestParams

Parameters for retrieving a specific prompt

GetPromptResult

GetTaskMethod

GetTaskParams

GetTaskResult

Response to a tasks/get request (spec GetTaskResult = Result & DetailedTask).

Icon

A URL pointing to an icon resource or a base64-encoded data URI.

ImageContent

Image content with base64-encoded data (spec ImageContent).

Implementation

InitializeRequestParams

Parameters sent by a client when initializing a connection to an MCP server.

InitializeResult

The server’s response to an initialization request.

InitializeResultMethod

InitializedNotificationMethod

InputRequiredResult

A result indicating that additional input is needed before the request can be completed.

IntegerSchema

Schema definition for integer properties.

IntegerTypeConst

JsonContent

JsonRpcError

JsonRpcNotification

JsonRpcRequest

JsonRpcResponse

JsonRpcVersion2_0

LegacyEnumSchema

Legacy enum schema, keep for backward compatibility

ListPromptsRequestMethod

ListPromptsResult

ListResourceTemplatesRequestMethod

ListResourceTemplatesResult

ListResourcesRequestMethod

ListResourcesResult

ListRootsRequestMethod

ListRootsResultDeprecated

ListToolsRequestMethod

ListToolsResult

LoggingMessageNotificationMethod

LoggingMessageNotificationParamDeprecated

Parameters for a logging message notification

MetaObject

General-purpose _meta map (spec MetaObject).

ModelHintDeprecated

A hint suggesting a preferred model name or family.

ModelPreferencesDeprecated

Preferences for model selection and behavior in sampling requests.

MultiSelect

Marker type for multi-select enum builder

Notification

NotificationMetaObject

The _meta map carried by notifications (spec NotificationMetaObject).

NotificationNoParam

NumberSchema

Schema definition for number properties (floating-point).

NumberTypeConst

ObjectTypeConst

PaginatedRequestParams

PingRequestMethod

ProgressNotificationMethod

ProgressNotificationParam

ProgressToken

A token used to track the progress of long-running operations.

Prompt

A prompt or prompt template that the server offers (spec Prompt).

PromptArgument

Describes an argument that a prompt can accept (spec PromptArgument).

PromptListChangedNotificationMethod

PromptMessage

A message returned as part of a prompt (spec PromptMessage).

PromptReference

PromptsCapability

ProtocolVersion

Represents the MCP protocol version used for communication.

ReadResourceRequestMethod

ReadResourceRequestParams

Parameters for reading a specific resource

ReadResourceResult

Result containing the contents of a read resource

Request

Represents a JSON-RPC request with method, parameters, and extensions.

RequestMetaObject

The _meta map carried by requests (spec RequestMetaObject).

RequestNoParam

RequestOptionalParam

Resource

A known resource that the server is capable of reading (spec Resource).

ResourceListChangedNotificationMethod

ResourceTemplate

A template description for resources available on the server (spec ResourceTemplate).

ResourceTemplateReference

ResourceUpdatedNotificationMethod

ResourceUpdatedNotificationParam

Parameters for a resource update notification

ResourcesCapability

ResultType

Indicates the type of a result object, allowing the client to determine how to parse the response.

RootDeprecated

RootsCapabilities

Roots capability. Deprecated by SEP-2577; remains functional and will be removed in a future release. See https://github.com/modelcontextprotocol/modelcontextprotocol/pull/2577.

RootsListChangedNotificationMethod

SamplingCapability

Sampling capability with optional sub-capabilities (SEP-1577).

SamplingMessageDeprecated

A message in a sampling conversation, containing a role and content.

ServerCapabilities

Builder

ServerCapabilitiesBuilder

ServerCapabilitiesBuilderState

ServerPeerInfo

Information negotiated about a server peer.

SetLevelRequestMethod

SetLevelRequestParamsDeprecated

Parameters for setting the logging level

SingleSelect

Marker type for single-select enum builder

StringSchema

Schema definition for string properties.

StringTypeConst

SubscribeRequestMethod

SubscribeRequestParams

Parameters for subscribing to resource updates

SubscriptionFilter

Notification categories a client opts in to on a subscriptions/listen stream.

SubscriptionFilterBuilder

Builder for SubscriptionFilter.

SubscriptionsAcknowledgedNotificationMethod

SubscriptionsAcknowledgedNotificationParams

Parameters reporting the accepted subset of a subscription filter.

SubscriptionsListenRequestMethod

SubscriptionsListenRequestParams

Parameters for opening a long-lived notification subscription.

SubscriptionsListenResult

Final response indicating that a subscription ended gracefully.

SubscriptionsListenResultMeta

Metadata on the final result of a subscriptions/listen request.

Task

Operational metadata about ongoing work (spec Task, SEP-2663).

TaskAckResult

Empty acknowledgement for tasks/update and tasks/cancel (SEP-2663).

TaskStatusNotificationMethod

TaskStatusNotificationParams

Parameters for a task status notification (spec TaskStatusNotificationParams).

TextContent

Text content block (spec TextContent).

TitledItems

Items for titled multi-select options

TitledMultiSelectEnumSchema

Multi-select titled options

TitledSingleSelectEnumSchema

Titled single-select

Tool

A tool that can be used by a model.

ToolAnnotations

Additional properties describing a Tool to clients.

ToolChoiceDeprecated

Tool choice configuration (SEP-1577).

ToolListChangedNotificationMethod

ToolResultContentDeprecated

Tool execution result in user message (SEP-1577).

ToolUseContentDeprecated

Tool call request from assistant (SEP-1577).

ToolsCapability

UnsubscribeRequestMethod

UnsubscribeRequestParams

Parameters for unsubscribing from resource updates

UntitledItems

Items for untitled multi-select options

UntitledMultiSelectEnumSchema

Multi-select untitled options

UntitledSingleSelectEnumSchema

Untitled single-select

UpdateTaskMethod

UpdateTaskParams

Parameters for tasks/update (SEP-2663): deliver responses to outstanding in-task server-to-client requests surfaced via tasks/get inputRequests.

UrlElicitationCapability

Capability for URL mode elicitation.

Enums

CacheScope

Scope describing who may cache cacheable list/read results (SEP-2549).

CallToolResponse

Result of a tools/call request, including the MRTR intermediate result.

ClientNotification

ClientRequest

ClientResult

ContentBlock

Unified content block union (spec ContentBlock).

ContextInclusion

Specifies how much context should be included in sampling requests.

ElicitRequestParams

Parameters for creating an elicitation request to gather user input.

ElicitationAction

Represents the possible actions a user can take in response to an elicitation request.

EnumSchema

Compliant with MCP 2025-06-18 specification for elicitation schemas. Enums must have string type for values and can optionally include human-readable names.

GetPromptResponse

Result of a prompts/get request, including the MRTR intermediate result.

IconTheme

Icon themes supported by the MCP specification

InputRequest

A server-initiated request that can appear inside InputRequests.

JsonRpcMessage

Represents any JSON-RPC message that can be sent or received.

LoggingLevelDeprecated

Logging levels supported by the MCP protocol

MultiSelectEnumSchema

Multi-select enum options

NumberOrString

A flexible identifier type that can be either a number or a string.

PrimitiveSchemaDefinition

Primitive schema definition for elicitation properties.

ReadResourceResponse

Result of a resources/read request, including the MRTR intermediate result.

Reference

ResourceContents

The contents of a specific resource or sub-resource.

Role

Represents the role of a participant in a conversation or message exchange.

SamplingContent

Single or array content wrapper (SEP-1577).

SamplingMessageContentBlockDeprecated

Content types for sampling messages (SEP-1577).

ServerNotification

ServerRequest

ServerResult

SingleSelectEnumSchema

Combined single-select

StringFormat

String format types allowed by the MCP specification.

TaskPayload

Status-specific payload carried alongside the base Task fields in a DetailedTask.

TaskStatus

Canonical task lifecycle status (SEP-2663).

ToolChoiceMode

Tool selection mode (SEP-1577).

Constants

DEFAULT_MRTR_MAX_ROUNDS

Default maximum number of MRTR rounds a high-level client call will drive.

TASKS_EXTENSION_ID

Extension identifier for the MCP Tasks extension (SEP-2663).

Traits

ConstString

GetExtensions

GetMeta

Access to the metadata carried by a message envelope’s Extensions.

IntoContents

Types that can be converted into a list of content blocks.

RequestParamsMeta

Trait for request params that contain the _meta field.

Functions

object

unwrap the JsonObject under serde_json::Value

Type Aliases

CallToolRequest

Request to call a specific tool

CancelTaskRequest

CancelledNotification

Cancellation

ClientConfig

A client’s own configuration: the protocol version, capabilities, and implementation identity it advertises to servers.

ClientInfoDeprecated

Deprecated alias for ClientConfig.

ClientJsonRpcMessage

CompleteRequest

CreateMessageRequestDeprecated

Cursor

DiscoverRequest

A request for the server’s supported protocol versions and capabilities.

ElicitRequest

Request type for creating an elicitation to gather user input

EmptyResult

Empty result

ExperimentalCapabilities

ExtensionCapabilities

MCP extension capabilities map.

GetPromptRequest

Request to get a specific prompt

GetTaskRequest

InitializeRequest

Initialization

InitializedNotification

This notification is sent from the client to the server after initialization has finished.

InputRequests

A map of server-initiated requests that the client must fulfill.

InputResponses

A map of client responses to server-initiated requests.

JsonObject

A JSON object type alias for convenient handling of JSON data.

ListPromptsRequest

Request to list all available prompts from a server

ListResourceTemplatesRequest

Request to list all available resource templates from a server

ListResourcesRequest

Request to list all available resources from a server

ListRootsRequestDeprecated

ListToolsRequest

Request to list all available tools from a server

LoggingMessageNotificationDeprecated

Notification containing a log message

PingRequest

ProgressNotification

PromptListChangedNotification

Notification sent when the list of available prompts changes

ReadResourceRequest

Request to read a specific resource

RequestId

Type alias for request identifiers used in JSON-RPC communication.

ResourceListChangedNotification

Notification sent when the list of available resources changes

ResourceUpdatedNotification

Notification sent when a subscribed resource is updated

RootsListChangedNotification

ServerConfig

A server’s own configuration: the protocol version, capabilities, implementation identity, and instructions it advertises to clients.

ServerInfoDeprecated

Deprecated alias for ServerConfig.

ServerJsonRpcMessage

SetLevelRequestDeprecated

Request to set the logging level

SubscribeRequestDeprecated

Request to subscribe to resource updates

SubscriptionsAcknowledgedNotification

First notification sent on an established subscription stream.

SubscriptionsListenRequest

Request that opens a long-lived notification subscription.

TaskStatusNotification

ToolListChangedNotification

Notification sent when the list of available tools changes

UnsubscribeRequestDeprecated

Request to unsubscribe from resource updates

UpdateTaskRequest