@modelcontextprotocol/conformance

MCP Conformance Test Framework

A framework for testing MCP (Model Context Protocol) client and server implementations against the specification.

[!WARNING] This repository is a work in progress and is unstable. Join the conversation in the #conformance-testing-wg in the MCP Contributors discord.

For SDK maintainers: See SDK Integration Guide for a streamlined guide on integrating conformance tests into your SDK repository.

Quick Start

Testing Clients

# Using the everything-client (recommended)
npx @modelcontextprotocol/conformance client --command "tsx examples/clients/typescript/everything-client.ts" --scenario initialize

# Run an entire suite of tests
npx @modelcontextprotocol/conformance client --command "tsx examples/clients/typescript/everything-client.ts" --suite auth

Testing Servers

# Run all server scenarios (default)
npx @modelcontextprotocol/conformance server --url http://localhost:3000/mcp

# Run a single scenario
npx @modelcontextprotocol/conformance server --url http://localhost:3000/mcp --scenario server-initialize

List Available Scenarios

npx @modelcontextprotocol/conformance list

Overview

The conformance test framework validates MCP implementations by:

For Clients:

• Starting a test server for the specified scenario
• Running the client implementation with the test server URL
• Capturing MCP protocol interactions
• Running conformance checks against the specification
• Generating detailed test results

For Servers:

• Connecting to the running server as an MCP client
• Sending test requests and capturing responses
• Running conformance checks against server behavior
• Generating detailed test results

Usage

Client Testing

npx @modelcontextprotocol/conformance client --command "<client-command>" --scenario <scenario-name> [options]

Options:

• --command - The command to run your MCP client (can include flags)
• --scenario - The test scenario to run (e.g., "initialize")
• --suite - Run a suite of tests in parallel (e.g., "auth")
• --expected-failures <path> - Path to YAML baseline file of known failures (see Expected Failures)
• --timeout - Timeout in milliseconds (default: 30000)
• --verbose - Show verbose output

The framework appends <server-url> as an argument to your command and sets the MCP_CONFORMANCE_SCENARIO environment variable to the scenario name. For scenarios that require additional context (e.g., client credentials), the MCP_CONFORMANCE_CONTEXT environment variable contains a JSON object with scenario-specific data.

Server Testing

npx @modelcontextprotocol/conformance server --url <url> [--scenario <scenario>]

Options:

• --url - URL of the server to test
• --scenario <scenario> - Test scenario to run (e.g., "server-initialize"). Runs all available scenarios by default
• --suite <suite> - Suite to run: "active" (default), "all", or "pending"
• --expected-failures <path> - Path to YAML baseline file of known failures (see Expected Failures)
• --verbose - Show verbose output

Test Results

Client Testing - Results are saved to results/<scenario>-<timestamp>/:

• checks.json - Array of conformance check results with pass/fail status
• stdout.txt - Client stdout output
• stderr.txt - Client stderr output

Server Testing - Results are saved to results/server-<scenario>-<timestamp>/:

• checks.json - Array of conformance check results with pass/fail status

Expected Failures

SDKs that don't yet pass all conformance tests can specify a baseline of known failures. This allows running conformance tests in CI without failing, while still catching regressions.

Create a YAML file listing expected failures by mode:

# conformance-baseline.yml
server:
  - tools-call-with-progress
  - resources-subscribe
client:
  - sse-retry

Then pass it to the CLI:

npx @modelcontextprotocol/conformance server --url http://localhost:3000/mcp --expected-failures ./conformance-baseline.yml

Exit code behavior:

Scenario Result	In Baseline?	Outcome
Fails	Yes	Exit 0 — expected failure
Fails	No	Exit 1 — unexpected regression
Passes	Yes	Exit 1 — stale baseline, remove the entry
Passes	No	Exit 0 — normal pass

This ensures:

• CI passes when only known failures occur
• CI fails on new regressions (unexpected failures)
• CI fails when a fix lands but the baseline isn't updated (stale entries)

GitHub Action

This repo provides a composite GitHub Action so SDK repos don't need to write their own conformance scripts.

Server Testing

steps:
  - uses: actions/checkout@v4

  # Start your server (SDK-specific)
  - run: |
      my-server --port 3001 &
      timeout 15 bash -c 'until curl -s http://localhost:3001/mcp; do sleep 0.5; done'

  - uses: modelcontextprotocol/conformance@v0.1.11
    with:
      mode: server
      url: http://localhost:3001/mcp
      expected-failures: ./conformance-baseline.yml # optional

Client Testing

steps:
  - uses: actions/checkout@v4

  - uses: modelcontextprotocol/conformance@v0.1.11
    with:
      mode: client
      command: 'python tests/conformance/client.py'
      expected-failures: ./conformance-baseline.yml # optional

Action Inputs

Input	Required	Description
mode	Yes	server or client
url	Server mode	URL of the server to test
command	Client mode	Command to run the client under test
expected-failures	No	Path to YAML baseline file
suite	No	Test suite to run
scenario	No	Run a single scenario by name
timeout	No	Timeout in ms for client tests (default: 30000)
verbose	No	Show verbose output (default: false)
node-version	No	Node.js version (default: 20)

Example Clients

• examples/clients/typescript/everything-client.ts - Single client that handles all scenarios based on scenario name (recommended)
• examples/clients/typescript/test1.ts - Simple MCP client (for reference)
• examples/clients/typescript/auth-test.ts - Well-behaved OAuth client (for reference)

Available Scenarios

Client Scenarios

• initialize - Tests MCP client initialization handshake
  • Validates protocol version
  • Validates clientInfo (name and version)
  • Validates server response handling
• tools-call - Tests tool invocation
• auth/basic-dcr - Tests OAuth Dynamic Client Registration flow
• auth/basic-metadata-var1 - Tests OAuth with authorization metadata

Server Scenarios

Run npx @modelcontextprotocol/conformance list --server to see all available server scenarios, including:

• server-initialize - Tests server initialization and capabilities
• tools-list - Tests tool listing endpoint
• tools-call-* - Various tool invocation scenarios
• resources-* - Resource management scenarios
• prompts-* - Prompt management scenarios

SDK Tier Assessment

The tier-check subcommand evaluates an MCP SDK repository against SEP-1730 (the SDK Tiering System):

# Without conformance tests (fastest)
gh auth login
npm run --silent tier-check -- --repo modelcontextprotocol/typescript-sdk --skip-conformance

# With conformance tests (start the everything server first)
npm run --silent tier-check -- \
  --repo modelcontextprotocol/typescript-sdk \
  --conformance-server-url http://localhost:3000/mcp

For a full AI-assisted assessment with remediation guide, use Claude Code:

/mcp-sdk-tier-audit <local-sdk-path> <conformance-server-url>

See .claude/skills/mcp-sdk-tier-audit/README.md for full documentation.

Architecture

See src/runner/DESIGN.md for detailed architecture documentation.

Key Components

• Runner (src/runner/) - Orchestrates test execution and result generation
  • client.ts - Client testing implementation
  • server.ts - Server testing implementation
  • utils.ts - Shared utilities
  • index.ts - Public API exports
• CLI (src/index.ts) - Command-line interface using Commander.js
• Scenarios (src/scenarios/) - Test scenarios with expected behaviors
• Checks (src/checks/) - Conformance validation functions
• Types (src/types.ts) - Shared type definitions

Adding New Scenarios

• Create a new directory in src/scenarios/<scenario-name>/
• Implement the Scenario interface with start(), stop(), and getChecks()
• Register the scenario in src/scenarios/index.ts

See src/scenarios/initialize/ for a reference implementation.