mcp_client library

Kernel sub-barrel for outbound MCP client usage.

mcp_client is exposed through a dedicated entry point (rather than the main brain_kernel.dart barrel) because its model classes — Content / TextContent / ImageContent / CallToolResult / transport configs — collide pervasively with mcp_server's same-named classes. Rolling them into the main barrel forces every domain consumer to disambiguate. Splitting the surfaces keeps the main barrel clean for the typical builder usage (server-side MCP + bundle + LLM) while still letting tools that genuinely need outbound clients (inspector probes, cross-server wiring) reach the types through the kernel.

Usage:

import 'package:brain_kernel/mcp_client.dart';

final result = await McpClient.createAndConnect(
  config: const McpClientConfig(...),
);
if (result.content.first is TextContent) { ... }

Domain code that imports both brain_kernel.dart (for the server / bundle types) and this file should use a prefix on one of them to silence the expected collisions on Content / etc.

Classes

AudioContent: Audio content (spec 2025-03-26+).
AuthenticatedEventSource: Authenticated EventSource implementation
AuthServerMetadata: Authorization server metadata (RFC8414)
CachedResource: Cached resource item for performance optimization
CallToolRequest: Call tool request
CallToolResult: Tool call result. Spec 2025-06-18 added structuredContent (paired with Tool.outputSchema).
CancelRequestNotification: Cancel request notification
Client: Main MCP Client class that handles all client-side protocol operations
ClientCapabilities: Client capabilities configuration
ClientInfo: Client information (2025-03-26 compliant)
ClientTransport: Abstract base class for client transport implementations
CompletionRequest: Completion request
CompletionResult: Completion result
CompressedEventSource: Compressed EventSource implementation
Connected: The connection is established and ready
Connecting: The connection is in the process of connecting
ConnectionError: The connection has failed with an error
ConnectionState: Represents the various states of an MCP connection
Content: Base class for all MCP content types (2025-03-26 compliant)
CreateMessageRequest: Create message request for sampling
CreateMessageResult: Create message result from sampling
Disconnected: The connection is disconnected
Disconnecting: The connection is in the process of disconnecting
Failure<T, E extends Object>: Represents a failed result
GetPromptRequest: Get prompt request
GetPromptResult: Get prompt result
HeartbeatConfig: Heartbeat configuration
HeartbeatEventSource: Heartbeat-enabled EventSource implementation
HeartbeatStats: Heartbeat statistics
HttpOAuthClient: HTTP-based OAuth 2.1 client implementation
ImageContent: Image content representation
InitializeRequest: Initialize request
InitializeResult: Initialize result
JsonRpcMessage: JSON-RPC message
Level: Levels to control logging output. Logging can be enabled to include all levels above certain Level. Levels are ordered using an integer value Level.value. The predefined Level constants below are sorted as follows (in descending order): Level.SHOUT, Level.SEVERE, Level.WARNING, Level.INFO, Level.CONFIG, Level.FINE, Level.FINER, Level.FINEST, and Level.ALL.
ListPromptsResult: List prompts result
ListResourcesResult: List resources result
ListToolsResult: List tools result
Logger: Use a Logger to log debug messages.
LogMessageNotification: Log message notification
LogRecord: A log entry representation used to propagate information from Logger to individual handlers.
McpClient: Modern MCP Client factory with enhanced error handling and configuration
McpClientConfig: Configuration for creating MCP clients
McpProtocol: MCP protocol versions and constants
Message: Message model for prompt system
ModelHint: Model hint for sampling
ModelPreferences: Model preferences for sampling
OAuthClient: OAuth client interface
OAuthConfig: OAuth 2.1 authentication configuration
OAuthError: OAuth error response
OAuthToken: OAuth 2.1 token response
OAuthTokenManager: OAuth token manager with automatic refresh
PendingOperation: Pending operation for cancellation support
ProgressNotification: Progress notification
ProgressUpdate: Progress update for long-running operations
Prompt: Prompt definition
PromptArgument: Prompt argument definition
PromptsListChangedNotification: Prompts list changed notification
ProtocolCapabilities: Protocol capabilities
ReadResourceRequest: Read resource request
ReadResourceResult: Resource read result
Resource: Resource definition
ResourceContent: Resource content representation
ResourceContentInfo: Resource content
ResourceLinkContent: Resource link content (spec 2025-06-18+).
ResourcesListChangedNotification: Resources list changed notification
ResourceTemplate: Resource template definition
ResourceUpdatedNotification: Resource updated notification
Result<T, E extends Object>: A sealed class representing the result of an operation that can succeed or fail
Results: Utility functions for working with Results
Root: Root definition for filesystem access
Semaphore: Semaphore for controlling concurrent requests
ServerCapabilities: Server capabilities
ServerHealth: Server health information
ServerInfo: Server information (2025-03-26 compliant)
SseAuthClientTransport: SSE Transport with Bearer Token Authentication
SseClientTransport: Transport implementation using Server-Sent Events (SSE) over HTTP
SseCompressedClientTransport: SSE Transport with automatic compression support
SseHeartbeatClientTransport: SSE Transport with heartbeat monitoring
SseTransportConfig
StdioClientTransport: Transport implementation using standard input/output streams
StdioTransportConfig
StreamableHttpClientTransport: Streamable HTTP client transport for MCP
StreamableHttpTransportConfig
Success<T, E extends Object>: Represents a successful result
TextContent: Text content representation
TokenLifecycleEvent: Token lifecycle event.
Tool: Tool definition. Spec 2025-06-18+ added outputSchema, _meta, and the title display name (separate from programmatic name). Spec 2025-11-25+ added icons.
ToolCallTracking: Class to hold result of a tracked tool call
ToolMetadata: Lightweight tool metadata (name + description only) Used for token-efficient LLM context in deferred loading mode
ToolRegistry: Cache layer for tool definitions Provides metadata extraction and full schema lookup LLM-agnostic: can be used without mcp_llm
ToolsListChangedNotification: Tools list changed notification
TransportConfig: Configuration for transport connections

Enums

CompressionType: Compression types supported
ConnectionHealth: Connection health status
DisconnectReason: Reason for disconnection
MCPContentType
McpLogLevel: Log levels for MCP protocol
MessageRole: Base content type enum for MCP
OAuthGrantType: OAuth 2.1 grant types supported by MCP
TokenEventType: Token lifecycle event types.

Extensions

ClientToolMetadataExtension on Client: Extension on Client for easy metadata access in deferred loading mode
FutureResultExtensions on Future<Result<T, E>>: Extension methods for Future<Result>
LoggerExtensions on Logger

Constants

defaultLevel → const Level: The default Level.

Properties

hierarchicalLoggingEnabled ↔ bool: Whether to allow fine-grain logging and configuration of loggers in a hierarchy.
getter/setter pair
recordStackTraceAtLevel ↔ Level: Automatically record stack traces for any message of this level or above.
getter/setter pair

Typedefs

MCPClient = McpClient

Exceptions / Errors

McpError: Error class for MCP-related errors

mcp_client library

Classes

Enums

Extensions

Constants

Properties

Typedefs

Exceptions / Errors

brain_kernel package

mcp_client library