mcp_dart 2.3.0-dev.3

Dart and Flutter SDK for building Model Context Protocol (MCP) servers, clients, hosts, and AI tools.

MCP (Model Context Protocol) for Dart

mcp_dart is a dual-era Dart and Flutter SDK for MCP clients, servers, and AI hosts. It implements the complete core client/server wire surface of the locked release candidate for the MCP 2026-07-28 specification, retains the MCP 2025-11-25 feature set, and negotiates supported earlier initialization-based specifications.

Here, core means the normative wire requirements assigned to client and server roles by the pinned release-candidate specification. It excludes optional MCP extensions, host UI behavior, an authorization-server implementation, JSON Schema external-reference resolution, and custom JSON Schema vocabularies.

Important

The coordinated dev.3 prerelease pairs mcp_dart 2.3.0-dev.3 with mcp_dart_cli 0.2.0-dev.3. It passes the official alpha.9 MCP 2026-07-28 client suite, including all 25 authorization scenarios. Its server suite has three exact expected diagnostics because the published referee predates spec PR #3002; merged conformance PR #403 semantics pass locally. This is prerelease evidence, not a claim about the final specification, which has not shipped.

Preview requirements

Package	Minimum Dart SDK
mcp_dart 2.3.0-dev.3	3.4
mcp_dart_cli 0.2.0-dev.3	3.12

SDK-only generated projects retain the SDK's Dart 3.4 minimum. CLI projects use Dart 3.12 because the CLI and its toolchain target that release.

Install Dart from dart.dev.

Installation

Production channel

Use the latest stable package for production projects:

dart pub add mcp_dart

Evaluate the MCP 2026-07-28 preview

Select the prerelease explicitly:

dependencies:
  mcp_dart: ^2.3.0-dev.3

The preview snippets use the coordinated dev.3 package line. Production-channel users should follow the documentation for the version resolved in their own pubspec.lock. Package channels are separate from protocol profiles: McpProtocol.stable names the SDK's default compatibility policy, not package or wire-spec maturity.

Prerelease packages are published in order: SDK first, then CLI. Verify the requested version is available on pub.dev before installing the CLI or creating a clean consumer project.

For direct SDK integration, start with the getting-started guide. The CLI below is optional and provides scaffolding, inspection, and conformance commands.

What the SDK provides

• MCP servers, clients, and host integrations with null-safe Dart APIs.
• Core tools, resources, prompts, completion, elicitation, subscriptions, logging, roots, and sampling APIs with behavior selected for the negotiated protocol era. MCP 2026-07-28 logging is retained for compatibility but is deprecated upstream.
• Stdio, Streamable HTTP, IO stream, and custom transports.
• OAuth client discovery/PKCE hooks, server authentication callbacks, DNS rebinding protection, and strict Streamable HTTP validation.
• A Tasks extension implementation, MCP Apps metadata helpers, and generic extension negotiation. Extensions are separate from core protocol coverage.
• Automated MCP 2025-11-25 and MCP 2026-07-28 conformance, bidirectional published TypeScript beta interoperability, Python beta server interoperability with an exact pre-#3002 client-gap check, real-browser transport tests, a real Flutter Web service integration in Chrome, deterministic widget tests, and an independent pinned JSON Schema Test Suite gate.

MCP has three roles: a host owns the user experience, a client connects that host to one server, and a server exposes tools, resources, and prompts. A host can manage multiple clients and servers.

Protocol profiles

Profile	Protocol behavior
McpProtocol.stable	Default dual-era profile: prefer MCP 2026-07-28, then fall back to initialization-based MCP specifications; body-only discovery probes are bounded to 5 seconds
McpProtocol.legacy	Initialization-era profile: negotiate the MCP 2025-11-25, MCP 2025-06-18, MCP 2025-03-26, MCP 2024-11-05, or MCP 2024-10-07 specification
McpProtocol.require2026	Require MCP 2026-07-28 and reject legacy initialization

Use stableProtocolVersion for the official 2025-11-25 version, previewProtocolVersion for the MCP 2026-07-28 preview, and defaultProtocolVersion for this SDK preview's preferred version. latestInitializationProtocolVersion remains 2025-11-25 when the default profile falls back to the legacy lifecycle. For compatibility, latestProtocolVersion and supportedProtocolVersions retain their mcp_dart 2.2 initialization-era values; use allSupportedProtocolVersions for the dual-era list.

Select a profile only when you need to constrain negotiation:

final legacyClient = McpClient(
  const Implementation(name: 'my-client', version: '1.0.0'),
  options: const McpClientOptions(protocol: McpProtocol.legacy),
);

final strictPreviewServer = McpServer(
  const Implementation(name: 'my-server', version: '1.0.0'),
  options: const McpServerOptions(protocol: McpProtocol.require2026),
);

See the MCP 2026-07-28 transition guide for fallback rules and APIs specific to MCP 2026-07-28, or run the strict MCP 2026-07-28 example. Applications upgrading from the stable 2.2 line should also follow the 2.2 to 2.3 migration guide.

Quick start with the CLI

Install the matching preview CLI:

dart pub global activate mcp_dart_cli 0.2.0-dev.3
mcp_dart create my_server
cd my_server
mcp_dart inspect

The dev.3 CLI creates a project with mcp_dart: ^2.3.0-dev.3. The inspector launches the generated stdio server itself. After leaving the interactive inspector, you can run a single tool directly:

mcp_dart inspect --tool add --json-args '{"a": 1, "b": 2}'

Useful commands:

Command	Purpose
create	Scaffold a Dart MCP server using the SDK channel paired with the CLI
serve	Run a generated server over stdio or HTTP
doctor	Check project health and connectivity
inspect	Interactively use a server's capabilities
inspect-server	Produce a structured report for a live server
inspect-client	Run a stdio harness that inspects a connecting client
trace	Proxy and record a real stdio session
conformance	Run the repository's built-in protocol regression fixtures

See the CLI documentation for command options and scope.

Documentation

• Start: getting started, server guide, client guide, quick reference
• Upgrade: 2.2 to 2.3 migration guide, migration cookbooks, MCP 2026-07-28 transition guide
• Build: tools, transports, examples, MCP Apps
• Deploy: Streamable HTTP security, OAuth examples, Flutter recipes
• Verify: interop matrix, MCP 2025-11-25 coverage, MCP 2026-07-28 preview coverage, day-0 runbook

Standalone integration examples may declare newer Dart SDK requirements; check each example README before running it.

Authentication

StreamableHttpClientTransport supports OAuthClientProvider and optional authorization-code discovery. Servers can use authenticator or authenticationHandler and publish protected-resource metadata.

The checked-in OAuth examples store tokens in plaintext files for local learning. Production applications must use platform secure storage or an encrypted credential service. See the OAuth examples and Streamable HTTP authentication.

Do not expose example HTTP servers directly to untrusted networks. Production deployments should use TLS, authenticate requests, and configure the documented Host and Origin protections.

Platform support

Target	Stdio	Streamable HTTP	IO/custom stream
Dart VM / desktop server	Yes	Client and server	Yes
Browser / Flutter Web	No process spawning	Client	Yes
Flutter mobile	Only app-managed native helpers	Remote client	Yes
Flutter desktop	Local helper processes	Client and server	Yes

See Flutter host and client recipes for lifecycle and secure-storage guidance.

Choosing a Dart MCP package

The Dart team maintains dart_mcp in dart-lang/ai. Choose it when you prefer the Dart team's APIs. Choose mcp_dart when you need this SDK's transport, security, compatibility, extension, and inspection surface. Re-check both packages' current releases before a production decision.

Support

• Issues and bug reports
• SDK on pub.dev
• dev.3 API reference
• Changelog
• MCP 2026-07-28 RC
• MCP 2025-11-25 specification