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

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 final 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 current stable packages are `mcp_dart 2.4.1` and

> `mcp_dart_cli 0.2.0`; the CLI's `^2.3.0` SDK constraint accepts 2.4.

> Current source passes every scored requirement in the official alpha.11 MCP

> `2025-11-25` and `2026-07-28` client and server sets, including all 25

> required 2026 authorization scenarios, plus bidirectional published

> TypeScript SDK 2.0.0 and Python SDK 2.0.0 interoperability.

SDK Tier 1 target

The project is pursuing

MCP SDK Tier 1. Tier 1

is not yet claimed or assigned. The technical baseline is green; the remaining

official audit, repository-governance, and SDK Working Group steps are tracked

in the roadmap and

48-feature coverage inventory.

The public maintenance contract is documented in the

contribution guide, security policy,

dependency policy, and

versioning policy.

Requirements

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

Pin the stable SDK release

Pin the stable 2.4 line explicitly when reproducible dependency resolution is

important:

dependencies:
  mcp_dart: ^2.4.1

The snippets below use the current stable SDK line. Package versions

remain separate from protocol profiles: `McpProtocol.stable` names the SDK's

default compatibility policy.

The SDK and CLI are versioned independently. The stable CLI's `^2.3.0`

constraint remains compatible with the 2.4 SDK.

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.

• An experimental Tasks extension implementation, MCP Apps metadata helpers,

and generic extension negotiation. Extensions are separate from core

protocol coverage; Tasks is not an official extension or part of the SDK's

core conformance claim.

• Automated MCP 2025-11-25 and MCP 2026-07-28 conformance, bidirectional

published TypeScript SDK 2.0.0 interoperability, bidirectional Python SDK

2.0.0 interoperability, 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_dart 2.4.1` hardens Streamable HTTP access and JSON-RPC error

diagnostics and retains the deprecated, opt-in legacy HTTP+SSE client with

same-origin routing and bidirectional interoperability against official

TypeScript SDK 1.30.0 and Python SDK 2.0.0 peers.

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

Use `stableProtocolVersion` or `defaultProtocolVersion` for MCP `2026-07-28`.

`previewProtocolVersion` remains as a deprecated alias for applications built

against a 2.3 prerelease.

`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 strict2026Server = 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 stable CLI:

dart pub global activate mcp_dart_cli 0.2.0
mcp_dart create my_server
cd my_server
mcp_dart inspect

The `0.2.0` CLI creates a project with `mcp_dart: ^2.3.0`. 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:

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 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

Legacy HTTP+SSE is deprecated under MCP SEP-2596 and is retained only for

explicit compatibility. Use Streamable HTTP for new remote integrations.

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
• Contribution and issue-triage policy
• Security policy
• Dependency policy
• Versioning policy
• Tier 1 roadmap
• SDK on pub.dev
• 2.4.1 API reference
• Changelog
• MCP 2026-07-28 specification
• MCP 2025-11-25 specification