Client

Category: Mcp_client

Source: client.dart

MCP JSON-RPC client.

Speaks MCP over an injectable [JsonRpcTransport] from glue_server so the same client works against stdio, HTTP+SSE, WebSocket, or an in-memory transport in tests.

Responsibilities: • initialize handshake + protocol version negotiation • tools/list, tools/call with a concurrent-id pending map • rate-limit retry-once • notifications fan-out (tools/list_changed, future server events) • drop detection → pending calls fail with retryable metadata

Classes

McpNotification

A peer-side notification flowing from the server. tools/list_changed is the only one we currently care about, but we surface everything so callers can route as they like.

Constructor

const McpNotification({required this.method, this.params})

Properties

Property	Type	Description
method	String
params	Map<String, dynamic>?

McpCallFailure

Failure shape thrown by [McpClient.callTool] / [listTools] / [initialize] when the call cannot complete. The agent loop maps this onto ToolResult(success: false, ...).

Constructor

const McpCallFailure({
    required this.reason,
    this.code,
    this.message,
    this.retryable = false,
    this.wwwAuthenticate,
  })

Properties

Property	Type	Description
reason	String	Short machine reason. Stable. Drives metadata.
code	int?	JSON-RPC error code if this came from the server.
message	String?	Human-readable message.
retryable	bool	Whether the agent loop may retry the same call.
wwwAuthenticate	String?	Raw WWW-Authenticate header, when this failure originated from a 401 transport error. Consumed by the pool to drive RFC 9728 discovery and refresh-token grant.

Methods

String toString()

McpClient

Constructor

McpClient({
    required this.transport,
    this.clientInfo = const McpClientInfo(name: 'glue', version: '0.0.0'),
    this.clientCapabilities = const McpClientCapabilities(
      roots: McpRootsCapability(listChanged: true),
    ),
    this.callTimeout = const Duration(seconds: 30),
  })

Properties

Property	Type	Description
transport	JsonRpcTransport
clientInfo	McpClientInfo
clientCapabilities	McpClientCapabilities
callTimeout	Duration
notifications	Stream<McpNotification> get
initResult	McpInitializeResult? get	Set after a successful [initialize]. Null otherwise.
notifications	Stream<McpNotification> get
initResult	McpInitializeResult? get	Set after a successful [initialize]. Null otherwise.

Methods

Future<McpInitializeResult> initialize()

Sends initialize + notifications/initialized. Negotiates the protocol version per the design doc: equal → continue; older within minimum-supported → continue with downgrade; newer → continue, upgrade-tolerant; older than minimum → refuse.

Future<List<McpToolDescriptor>> listTools()

`Future<McpToolCallResult> callTool(

String name,
Map<String, dynamic> arguments,

)`

Calls a tool. On JSON-RPC rate-limit (-32011) we honour the hint and retry once. On transport drop, all pending calls (including this one) resolve with [McpCallFailure(retryable: true)].

Future<void> close()