mcp_dart_cli

Command-line tools for creating Dart MCP servers and inspecting, tracing, or regression-testing spec-compatible MCP servers and clients in any language.

Installation

With Dart 3.7 or later, install the stable CLI:

dart pub global activate mcp_dart_cli

Install the coordinated MCP 2026-07-28 preview explicitly:

dart pub global activate mcp_dart_cli 0.2.0-dev.2

Prerelease packages are published SDK first, then CLI. Confirm mcp_dart 2.3.0-dev.2 is available before installing this CLI preview.

Without Dart, install the latest stable standalone binary:

curl -fsSL https://raw.githubusercontent.com/leehack/mcp_dart/main/tool/install.sh | sh

Windows PowerShell:

irm https://raw.githubusercontent.com/leehack/mcp_dart/main/tool/install.ps1 | iex

Set MCP_DART_INSTALL_DIR to choose the install directory. Standalone installers and mcp_dart update follow stable GitHub releases. Automatic update checks are disabled in prerelease builds so a preview is never replaced by the stable channel; reinstall the desired prerelease explicitly.

Create a server

mcp_dart create my_server
cd my_server
mcp_dart serve

The dev.2 CLI writes mcp_dart: ^2.3.0-dev.2, the SDK channel tested with this CLI. A stable CLI selects its matching stable SDK. You can also supply a local Mason brick, Git URL, GitHub shorthand, or tree URL:

mcp_dart create my_server \
  --template owner/repo/path/to/brick@ref

Commands

Command	Purpose
create	Scaffold an MCP server project
serve	Run a generated server over stdio or HTTP
doctor	Check project setup and connectivity
inspect	Interactively list or invoke server primitives
inspect-server	Produce a structured report for a live server
inspect-client	Host a stdio harness that observes a connecting client
trace	Proxy stdio traffic and write a chronological JSON report
list-tools	Print a scriptable tool inventory
call-tool	Invoke one tool with JSON arguments
conformance	Run this package's built-in protocol regression fixtures
skills	Install or print the bundled MCP developer skill
update	Update a stable installation through its install channel

Run mcp_dart <command> --help for every option.

Inspect a server

Use inspect for ad hoc interaction:

# Project in the current directory
mcp_dart inspect
mcp_dart inspect --tool add --json-args '{"a": 1, "b": 2}'
mcp_dart inspect --resource manifest://app
mcp_dart inspect --prompt greeting --json-args '{"name": "World"}'

# Any stdio server
mcp_dart inspect -- npx -y @modelcontextprotocol/server-filesystem /tmp
mcp_dart inspect --env API_KEY=secret -- python server.py

# Streamable HTTP
mcp_dart inspect --url https://mcp.example.com/mcp

Use inspect-server for a pass/warning/fail report suitable for review or CI:

mcp_dart inspect-server --json -- node dist/server.js
mcp_dart inspect-server -- python server.py
mcp_dart inspect-server --json --url http://localhost:3000/mcp

Optional probe configuration supplies real arguments without guessing or invoking every advertised operation:

{
  "tools": [{"name": "search", "arguments": {"query": "mcp"}}],
  "resource": {"uri": "file:///tmp/example.txt", "subscribe": false},
  "prompt": {"name": "summarize", "arguments": {"topic": "MCP"}},
  "task": {
    "tool": "long_running",
    "arguments": {"duration": 250},
    "ttl": 60000,
    "cancel": false
  }
}

mcp_dart inspect-server --json --probe-config probes.json -- node server.js

Warnings fail only with --strict. The inspector exercises advertised and safely configurable behavior; it does not certify complete spec compliance. See the inspection coverage and limits.

Inspect a client or host

inspect-client acts as a temporary stdio MCP server. Point a client or host at this command and write the report outside stdout, which is reserved for MCP:

mcp_dart inspect-client --report /tmp/mcp-client-report.json

The harness is passive by default. Add --active-probes only when you intentionally want it to call legacy roots/list, sampling/createMessage, and elicitation/create; those probes can expose local paths, incur model cost, or open user interface.

The harness supports stateless server/discover and legacy initialization. It records client metadata, capabilities, JSON-RPC shape, and use of the exposed test tool, resource, and prompt. For legacy clients, it can actively probe advertised roots, sampling, and elicitation.

Trace stdio traffic

Configure a client to launch mcp_dart trace in place of its server, then put the real server command after --:

mcp_dart trace --report /tmp/mcp-trace.json -- node server.js

The proxy keeps protocol frames on stdout, forwards server stderr, and records raw frames, parsed messages, methods, IDs, timing, and parse errors.

Inspection and trace reports can contain credentials, tool arguments/results, prompt or resource content, and other sensitive data. Store them with restricted permissions, never commit or upload them unreviewed, and delete them when done.

Scriptable tool smoke tests

mcp_dart list-tools --json -- node dist/server.js
mcp_dart list-tools --url http://localhost:3000/mcp

mcp_dart call-tool add \
  --json --json-args '{"a": 2, "b": 3}' -- node dist/server.js
mcp_dart call-tool search \
  --url http://localhost:3000/mcp --json-args '{"q": "mcp"}'

call-tool exits non-zero when the MCP result has isError: true.

Built-in conformance fixtures

conformance runs this repository's MCP 2025-11-25 and 2026-07-28 wire regression cases, including malformed JSON-RPC, ID/token preservation, negotiation, capabilities, stateless metadata, task metadata, and deterministic fuzz cases.

mcp_dart conformance --suite all
mcp_dart conformance --suite spec
mcp_dart conformance --case jsonrpc.preserves-string-response-id
mcp_dart conformance --fuzz --iterations 64
mcp_dart conformance --json

This is a package regression gate, not a live certification scanner. Combine it with live inspection, protocol logs, official conformance, and cross-SDK tests.

Serve, doctor, update, and skills

mcp_dart serve --transport stdio
mcp_dart serve --transport http --host 127.0.0.1 --port 3000
mcp_dart doctor
mcp_dart update
mcp_dart skills install

For compiled stable binaries, update downloads the matching asset from the latest stable CLI GitHub release. Pub-installed stable CLIs delegate to pub. Prerelease builds require an explicit reinstall.

Development and release validation

Run package tests from packages/mcp_dart_cli:

dart test

Validate the exported CLI package from the repository root:

dart run tool/validate_cli_publish.dart

Before publishing the CLI, validate against the already-published coordinated SDK rather than the monorepo override:

dart run tool/validate_cli_publish.dart --published-sdk
dart pub global activate pana
cd packages/mcp_dart_cli
dart pub global run pana --no-warning --exit-code-threshold 0

Require the full 160/160 score before publishing.

See CONTRIBUTING.md for contribution instructions.