data class CallToolResult(val content: List<ContentBlock>, val isError: Boolean? = null, val structuredContent: JsonObject? = null, val meta: JsonObject? = null) : ServerResult

The server's response to a CallToolRequest.

CancelledNotification

@Serializable

data class CancelledNotification(val params: CancelledNotificationParams) : ClientNotification, ServerNotification

This notification can be sent by either side to indicate that it is cancelling a previously-issued request.

CancelledNotificationParams

@Serializable

data class CancelledNotificationParams(val requestId: RequestId, val reason: String? = null, val meta: JsonObject? = null) : NotificationParams

Parameters for a notifications/cancelled notification.

ClientCapabilities

@Serializable

data class ClientCapabilities(val sampling: JsonObject? = null, val roots: ClientCapabilities.Roots? = null, val elicitation: JsonObject? = null, val experimental: JsonObject? = null)

Capabilities that a client may support.

ClientCapabilitiesBuilder

class ClientCapabilitiesBuilder

DSL builder for constructing ClientCapabilities instances.

ClientNotification

@Serializable(with = ClientNotificationPolymorphicSerializer::class)

sealed interface ClientNotification : Notification

Represents a notification sent by the client.

ClientRequest

@Serializable

sealed interface ClientRequest : Request

Represents a request sent by the client.

ClientResult

@Serializable(with = ClientResultPolymorphicSerializer::class)

sealed interface ClientResult : RequestResult

CompleteRequest

@Serializable

data class CompleteRequest(val params: CompleteRequestParams) : ClientRequest

A request from the client to the server to ask for completion options.

CompleteRequestBuilder

class CompleteRequestBuilder : RequestBuilder

DSL builder for constructing CompleteRequest instances.

CompleteRequestParams

@Serializable

data class CompleteRequestParams(val argument: CompleteRequestParams.Argument, val ref: Reference, val context: CompleteRequestParams.Context? = null, val meta: RequestMeta? = null) : RequestParams

Parameters for the completion request.

CompleteResult

@Serializable

data class CompleteResult(val completion: CompleteResult.Completion, val meta: JsonObject? = null) : ServerResult

The server's response to a CompleteRequest.

ContentBlock

@Serializable(with = ContentBlockPolymorphicSerializer::class)

sealed interface ContentBlock : WithMeta

ContentTypes

@Serializable

enum ContentTypes : Enum<ContentTypes>

CreateMessageRequest

@Serializable

data class CreateMessageRequest(val params: CreateMessageRequestParams) : ServerRequest

A request from the server to sample an LLM via the client.

CreateMessageRequestBuilder

class CreateMessageRequestBuilder : RequestBuilder

DSL builder for constructing CreateMessageRequest instances.

CreateMessageRequestParams

@Serializable

data class CreateMessageRequestParams(val maxTokens: Int, val messages: List<SamplingMessage>, val modelPreferences: ModelPreferences? = null, val systemPrompt: String? = null, val includeContext: IncludeContext? = null, val temperature: Double? = null, val stopSequences: List<String>? = null, val metadata: JsonObject? = null, val meta: RequestMeta? = null) : RequestParams

Parameters for a sampling/createMessage request.

CreateMessageResult

@Serializable

data class CreateMessageResult(val role: Role, val content: MediaContent, val model: String, val stopReason: StopReason? = null, val meta: JsonObject? = null) : ClientResult

The client's response to a CreateMessageRequest from the server.

CustomNotification

@Serializable

data class CustomNotification(val method: Method, val params: BaseNotificationParams? = null) : ClientNotification, ServerNotification

Represents a custom notification method that is not part of the core MCP specification.

CustomRequest

@Serializable

open class CustomRequest(val method: Method, val params: BaseRequestParams?) : Request

A custom request with a specified method.

ElicitRequest

@Serializable

data class ElicitRequest(val params: ElicitRequestParams) : ServerRequest

A request from the server to elicit additional information from the user via the client.

ElicitRequestBuilder

class ElicitRequestBuilder : RequestBuilder

DSL builder for constructing ElicitRequest instances.

ElicitRequestedSchemaBuilder

class ElicitRequestedSchemaBuilder

DSL builder for constructing ElicitRequestParams.RequestedSchema instances.

ElicitRequestParams

@Serializable

data class ElicitRequestParams(val message: String, val requestedSchema: ElicitRequestParams.RequestedSchema, val meta: RequestMeta? = null) : RequestParams

Parameters for an elicitation/create request.

ElicitResult

@Serializable

data class ElicitResult(val action: ElicitResult.Action, val content: JsonObject? = null, val meta: JsonObject? = null) : ClientResult

The client's response to an ElicitRequest.

EmbeddedResource

@Serializable

data class EmbeddedResource(val resource: ResourceContents, val annotations: Annotations? = null, val meta: JsonObject? = null) : ContentBlock

The contents of a resource, embedded into a prompt or tool call result.

EmptyResult

@Serializable

data class EmptyResult(val meta: JsonObject? = null) : ClientResult, ServerResult

An empty result for a request containing optional metadata.

GetPromptRequest

@Serializable

data class GetPromptRequest(val params: GetPromptRequestParams) : ClientRequest

Used by the client to get a prompt provided by the server.

GetPromptRequestBuilder

class GetPromptRequestBuilder : RequestBuilder

DSL builder for constructing GetPromptRequest instances.

GetPromptRequestParams

@Serializable

data class GetPromptRequestParams(val name: String, val arguments: Map<String, String>? = null, val meta: RequestMeta? = null) : RequestParams

Parameters for a prompts/get request.

GetPromptResult

@Serializable

data class GetPromptResult(val messages: List<PromptMessage>, val description: String? = null, val meta: JsonObject? = null) : ServerResult

The server's response to a GetPromptRequest from the client.

Icon

@Serializable

data class Icon(val src: String, val mimeType: String? = null, val sizes: List<String>? = null, val theme: Icon.Theme? = null)

An optionally sized icon that can be displayed in a user interface.

ImageContent

@Serializable

data class ImageContent(val data: String, val mimeType: String, val annotations: Annotations? = null, val meta: JsonObject? = null) : MediaContent

An image provided to or from an LLM.

ImageContentBuilder

class ImageContentBuilder : MediaContentBuilder

DSL builder for constructing ImageContent instances.

Implementation

@Serializable

data class Implementation(val name: String, val version: String, val title: String? = null, val websiteUrl: String? = null, val icons: List<Icon>? = null)

Describes an MCP (Model Context Protocol) implementation.

IncludeContext

@Serializable

enum IncludeContext : Enum<IncludeContext>

Specifies which MCP server context to include in the sampling request.

InitializedNotification

@Serializable

data class InitializedNotification(val params: BaseNotificationParams? = null) : ClientNotification

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

InitializeRequest

@Serializable

data class InitializeRequest(val params: InitializeRequestParams) : ClientRequest

This request is sent from the client to the server when it first connects, asking it to begin initialization.

InitializeRequestBuilder

class InitializeRequestBuilder : RequestBuilder

DSL builder for constructing InitializeRequest instances.

InitializeRequestParams

@Serializable

data class InitializeRequestParams(val protocolVersion: String, val capabilities: ClientCapabilities, val clientInfo: Implementation, val meta: RequestMeta? = null) : RequestParams

Parameters for an initialize request.

InitializeResult

@Serializable

data class InitializeResult(val protocolVersion: String = LATEST_PROTOCOL_VERSION, val capabilities: ServerCapabilities, val serverInfo: Implementation, val instructions: String? = null, val meta: JsonObject? = null) : ServerResult

After receiving an InitializeRequest from the client, the server sends this response.

JSONRPCError

@Serializable

data class JSONRPCError(val id: RequestId, val error: RPCError) : JSONRPCMessage

A response to a request that indicates an error occurred.

JSONRPCMessage

@Serializable(with = JSONRPCMessagePolymorphicSerializer::class)

sealed interface JSONRPCMessage

Base interface for all JSON-RPC 2.0 messages.

JSONRPCNotification

@Serializable

data class JSONRPCNotification(val method: String, val params: JsonElement? = null) : JSONRPCMessage

A notification which does not expect a response.

JSONRPCRequest

@Serializable

data class JSONRPCRequest @JvmOverloads constructor(val id: RequestId = RequestId(Uuid.random().toHexString()), val method: String, val params: JsonElement? = null) : JSONRPCMessage

A request that expects a response.

JSONRPCResponse

@Serializable

data class JSONRPCResponse(val id: RequestId, val result: RequestResult = EmptyResult()) : JSONRPCMessage

A successful (non-error) response to a request.

ListPromptsRequest

@Serializable

data class ListPromptsRequest(val params: PaginatedRequestParams? = null) : ClientRequest, PaginatedRequest

Sent from the client to request a list of prompts and prompt templates the server has.

ListPromptsRequestBuilder

class ListPromptsRequestBuilder : PaginatedRequestBuilder

DSL builder for constructing ListPromptsRequest instances.

ListPromptsResult

@Serializable

data class ListPromptsResult(val prompts: List<Prompt>, val nextCursor: String? = null, val meta: JsonObject? = null) : ServerResult, PaginatedResult

The server's response to a ListPromptsRequest from the client.

ListResourcesRequest

@Serializable

data class ListResourcesRequest(val params: PaginatedRequestParams? = null) : ClientRequest, PaginatedRequest

Sent from the client to request a list of resources the server has.

ListResourcesRequestBuilder

class ListResourcesRequestBuilder : PaginatedRequestBuilder

DSL builder for constructing ListResourcesRequest instances.

ListResourcesResult

@Serializable

data class ListResourcesResult(val resources: List<Resource>, val nextCursor: String? = null, val meta: JsonObject? = null) : ServerResult, PaginatedResult

The server's response to a ListResourcesRequest from the client.

ListResourceTemplatesRequest

@Serializable

data class ListResourceTemplatesRequest(val params: PaginatedRequestParams? = null) : ClientRequest, PaginatedRequest

Sent from the client to request a list of resource templates the server has.

ListResourceTemplatesRequestBuilder

class ListResourceTemplatesRequestBuilder : PaginatedRequestBuilder

DSL builder for constructing ListResourceTemplatesRequest instances.

ListResourceTemplatesResult

@Serializable

data class ListResourceTemplatesResult(val resourceTemplates: List<ResourceTemplate>, val nextCursor: String? = null, val meta: JsonObject? = null) : ServerResult, PaginatedResult

The server's response to a ListResourceTemplatesRequest from the client.

ListRootsRequest

@Serializable

data class ListRootsRequest(val params: BaseRequestParams? = null) : ServerRequest

Sent from the server to request a list of root URIs from the client.

ListRootsRequestBuilder

class ListRootsRequestBuilder : RequestBuilder

DSL builder for constructing ListRootsRequest instances.

ListRootsResult

@Serializable

data class ListRootsResult(val roots: List<Root>, val meta: JsonObject? = null) : ClientResult

The client's response to a ListRootsRequest from the server.

ListToolsRequest

@Serializable

data class ListToolsRequest(val params: PaginatedRequestParams? = null) : ClientRequest, PaginatedRequest

Sent from the client to request a list of tools the server has.

ListToolsRequestBuilder

class ListToolsRequestBuilder : PaginatedRequestBuilder

DSL builder for constructing ListToolsRequest instances.

ListToolsResult

@Serializable

data class ListToolsResult(val tools: List<Tool>, val nextCursor: String? = null, val meta: JsonObject? = null) : ServerResult, PaginatedResult

The server's response to a ListToolsRequest from the client.

LoggingLevel

@Serializable

enum LoggingLevel : Enum<LoggingLevel>

The severity of a log message.

LoggingMessageNotification

@Serializable

data class LoggingMessageNotification(val params: LoggingMessageNotificationParams) : ServerNotification

A notification of a log message passed from server to client.

LoggingMessageNotificationParams

@Serializable

data class LoggingMessageNotificationParams(val level: LoggingLevel, val data: JsonElement, val logger: String? = null, val meta: JsonObject? = null) : NotificationParams

Parameters for a notifications/message notification.

McpDsl

@DslMarker

annotation class McpDsl

DSL marker annotation for MCP builder classes.

McpException

class McpException @JvmOverloads constructor(val code: Int, message: String, val data: JsonElement? = null, cause: Throwable? = null) : Exception

Represents an error specific to the MCP protocol.

MediaContent

@Serializable(with = MediaContentPolymorphicSerializer::class)

sealed interface MediaContent : ContentBlock

MediaContentBuilder

abstract class MediaContentBuilder

Base DSL builder for constructing MediaContent instances.

Method

@Serializable(with = MethodSerializer::class)

sealed interface Method

Represents a method in the protocol, which can be predefined or custom.

ModelHint

@Serializable

data class ModelHint(val name: String?)

Hints to use for model selection.

ModelPreferences

@Serializable

data class ModelPreferences(val hints: List<ModelHint>? = null, val costPriority: Double? = null, val speedPriority: Double? = null, val intelligencePriority: Double? = null)

The server's preferences for model selection, requested of the client during sampling.

Notification

@Serializable(with = NotificationPolymorphicSerializer::class)

sealed interface Notification

Represents a notification in the protocol.

NotificationParams

@Serializable

sealed interface NotificationParams : WithMeta

Interface for notification parameter types.

PaginatedRequest

@Serializable

sealed interface PaginatedRequest : Request

Represents a request supporting pagination.

PaginatedRequestBuilder

abstract class PaginatedRequestBuilder : RequestBuilder

Base DSL builder for constructing paginated MCP request instances.

PaginatedRequestParams

@Serializable

data class PaginatedRequestParams(val cursor: String? = null, val meta: RequestMeta? = null) : RequestParams

Common parameters for paginated requests.

PaginatedResult

@Serializable

sealed interface PaginatedResult : RequestResult

Represents a request supporting pagination.

PingRequest

@Serializable

data class PingRequest(val params: BaseRequestParams? = null) : ClientRequest, ServerRequest

PingRequestBuilder

class PingRequestBuilder : RequestBuilder

DSL builder for constructing PingRequest instances.

Progress

@Serializable

class Progress(val progress: Double, val total: Double? = null, val message: String? = null)

Represents a progress notification.

ProgressNotification

@Serializable

data class ProgressNotification(val params: ProgressNotificationParams) : ClientNotification, ServerNotification

An out-of-band notification used to inform the receiver of a progress update for a long-running request.

ProgressNotificationParams

@Serializable

data class ProgressNotificationParams(val progressToken: ProgressToken, val progress: Double, val total: Double? = null, val message: String? = null, val meta: JsonObject? = null) : NotificationParams

Parameters for a notifications/progress notification.

ProgressToken

typealias ProgressToken = RequestId

A progress token, used to associate progress notifications with the original request.

Prompt

@Serializable

data class Prompt(val name: String, val description: String? = null, val arguments: List<PromptArgument>? = null, val title: String? = null, val icons: List<Icon>? = null, val meta: JsonObject? = null) : WithMeta

A prompt or prompt template that the server offers.

PromptArgument

@Serializable

data class PromptArgument(val name: String, val description: String? = null, val required: Boolean? = null, val title: String? = null)

Describes an argument that a prompt can accept.

PromptListChangedNotification

@Serializable

data class PromptListChangedNotification(val params: BaseNotificationParams? = null) : ServerNotification

An optional notification from the server to the client, informing it that the list of prompts it offers has changed.

PromptMessage

@Serializable

data class PromptMessage(val role: Role, val content: ContentBlock)

Describes a message returned as part of a prompt.

PromptReference

@Serializable

data class PromptReference(val name: String, val title: String? = null) : Reference

Identifies a prompt by reference.

ReadResourceRequest

@Serializable

data class ReadResourceRequest(val params: ReadResourceRequestParams) : ClientRequest

Sent from the client to the server to read a specific resource URI.

ReadResourceRequestBuilder

class ReadResourceRequestBuilder : RequestBuilder

DSL builder for constructing ReadResourceRequest instances.

ReadResourceRequestParams

@Serializable

data class ReadResourceRequestParams(val uri: String, val meta: RequestMeta? = null) : RequestParams

Parameters for a resources/read request.

ReadResourceResult

@Serializable

data class ReadResourceResult(val contents: List<ResourceContents>, val meta: JsonObject? = null) : ServerResult

The server's response to a ReadResourceRequest from the client.

Reference

@Serializable(with = ReferencePolymorphicSerializer::class)

sealed interface Reference

Base interface for reference types in the protocol.

ReferenceType

@Serializable

enum ReferenceType : Enum<ReferenceType>

Request

@Serializable(with = RequestPolymorphicSerializer::class)

sealed interface Request

Represents a request in the protocol.

RequestBuilder

abstract class RequestBuilder

Base DSL builder for constructing MCP request instances.

RequestId

@Serializable(with = RequestIdPolymorphicSerializer::class)

sealed interface RequestId

A uniquely identifying ID for a request in JSON-RPC.

RequestMeta

@JvmInline

@Serializable

value class RequestMeta(val json: JsonObject)

RequestMetaBuilder

class RequestMetaBuilder

DSL builder for constructing RequestMeta instances.

RequestParams

@Serializable

sealed interface RequestParams

RequestResult

@Serializable(with = RequestResultPolymorphicSerializer::class)

sealed interface RequestResult : WithMeta

Represents the result of a request, including additional metadata.

Resource

@Serializable

data class Resource(val uri: String, val name: String, val description: String? = null, val mimeType: String? = null, val size: Long? = null, val title: String? = null, val annotations: Annotations? = null, val icons: List<Icon>? = null, val meta: JsonObject? = null) : ResourceLike

A known resource that the server is capable of reading.

ResourceContents

@Serializable(with = ResourceContentsPolymorphicSerializer::class)

sealed interface ResourceContents : WithMeta

The contents of a specific resource or sub-resource.

ResourceLike

@Serializable

sealed interface ResourceLike : WithMeta

ResourceLink

@Serializable

data class ResourceLink(val name: String, val uri: String, val title: String? = null, val size: Long? = null, val mimeType: String? = null, val icons: List<Icon>? = null, val description: String? = null, val annotations: Annotations? = null, val meta: JsonObject? = null) : ContentBlock, ResourceLike

A resource that the server is capable of reading, included in a prompt or tool call result.

ResourceListChangedNotification

@Serializable

data class ResourceListChangedNotification(val params: BaseNotificationParams? = null) : ServerNotification

An optional notification from the server to the client, informing it that the list of resources it can read from has changed.

ResourceTemplate

@Serializable

data class ResourceTemplate(val uriTemplate: String, val name: String, val description: String? = null, val mimeType: String? = null, val title: String? = null, val annotations: Annotations? = null, val icons: List<Icon>? = null, val meta: JsonObject? = null) : WithMeta

A template description for resources available on the server.

ResourceTemplateReference

@Serializable

data class ResourceTemplateReference(val uri: String) : Reference

A reference to a resource or resource template definition.

ResourceUpdatedNotification

@Serializable

data class ResourceUpdatedNotification(val params: ResourceUpdatedNotificationParams) : ServerNotification

A notification from the server to the client, informing it that a resource has changed and may need to be read again.

ResourceUpdatedNotificationParams

@Serializable

data class ResourceUpdatedNotificationParams(val uri: String, val meta: JsonObject? = null) : NotificationParams

Parameters for a notifications/resources/updated notification.

Role

@Serializable

enum Role : Enum<Role>

The sender or recipient of messages and data in a conversation.

Root

@Serializable

data class Root(val uri: String, val name: String? = null, val meta: JsonObject? = null) : WithMeta

Represents a root directory or file that the server can operate on.

RootsListChangedNotification

@Serializable

data class RootsListChangedNotification(val params: BaseNotificationParams? = null) : ClientNotification

A notification from the client to the server, informing it that the list of roots has changed.

RPCError

@Serializable

data class RPCError(val code: Int, val message: String, val data: JsonElement? = null)

Error information for a failed JSON-RPC request.

SamplingMessage

@Serializable

data class SamplingMessage(val role: Role, val content: MediaContent)

Describes a message issued to or received from an LLM API.

SamplingMessageBuilder

class SamplingMessageBuilder

DSL builder for constructing lists of SamplingMessage instances.

ServerCapabilities

@Serializable

data class ServerCapabilities(val tools: ServerCapabilities.Tools? = null, val resources: ServerCapabilities.Resources? = null, val prompts: ServerCapabilities.Prompts? = null, val logging: JsonObject? = null, val completions: JsonObject? = null, val experimental: JsonObject? = null)

Capabilities that a server may support.

ServerNotification

@Serializable(with = ServerNotificationPolymorphicSerializer::class)

sealed interface ServerNotification : Notification

Represents a notification sent by the server.

ServerRequest

@Serializable

sealed interface ServerRequest : Request

Represents a request sent by the server.

ServerResult

@Serializable(with = ServerResultPolymorphicSerializer::class)

sealed interface ServerResult : RequestResult

SetLevelRequest

@Serializable

data class SetLevelRequest(val params: SetLevelRequestParams) : ClientRequest

A request from the client to the server to enable or adjust logging.

SetLevelRequestBuilder

class SetLevelRequestBuilder : RequestBuilder

DSL builder for constructing SetLevelRequest instances.

SetLevelRequestParams

@Serializable

data class SetLevelRequestParams(val level: LoggingLevel, val meta: RequestMeta? = null) : RequestParams

Parameters for a logging/setLevel request.

StopReason

@JvmInline

@Serializable

value class StopReason(val value: String)

SubscribeRequest

@Serializable

data class SubscribeRequest(val params: SubscribeRequestParams) : ClientRequest

Sent from the client to request resources/updated notifications from the server whenever a particular resource changes.

SubscribeRequestBuilder

class SubscribeRequestBuilder : RequestBuilder

DSL builder for constructing SubscribeRequest instances.

SubscribeRequestParams

@Serializable

data class SubscribeRequestParams(val uri: String, val meta: RequestMeta? = null) : RequestParams

Parameters for a resources/subscribe request.

TextContent

@Serializable

data class TextContent(val text: String, val annotations: Annotations? = null, val meta: JsonObject? = null) : MediaContent

Text provided to or from an LLM.

TextContentBuilder

class TextContentBuilder : MediaContentBuilder

DSL builder for constructing TextContent instances.

TextResourceContents

@Serializable

data class TextResourceContents(val text: String, val uri: String, val mimeType: String? = null, val meta: JsonObject? = null) : ResourceContents

Represents the text contents of a resource.

Tool

@Serializable

data class Tool(val name: String, val inputSchema: ToolSchema, val description: String? = null, val outputSchema: ToolSchema? = null, val title: String? = null, val annotations: ToolAnnotations? = null, val icons: List<Icon>? = null, val meta: JsonObject? = null) : WithMeta

Definition for a tool the client can call.

ToolAnnotations

@Serializable

data class ToolAnnotations(val title: String? = null, val readOnlyHint: Boolean? = null, val destructiveHint: Boolean? = null, val idempotentHint: Boolean? = null, val openWorldHint: Boolean? = null)

Additional properties describing a Tool to clients.

ToolListChangedNotification

@Serializable

data class ToolListChangedNotification(val params: BaseNotificationParams? = null) : ServerNotification

An optional notification from the server to the client, informing it that the list of tools it offers has changed.

ToolSchema

@Serializable