MCP Workbench — VS Code Extension

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Run, inspect, and validate MCP servers directly from VS Code.

Official IDE integration for MCP Workbench.

Overview

MCP Workbench for VS Code provides an integrated environment for running and validating MCP servers directly inside the editor.

• Run YAML-based MCP test specifications without leaving the editor
• View test results, assertion failures, and diffs in a dedicated tree view
• Failed assertions surface as Problems panel diagnostics with file locations
• Full execution logs streamed to the MCP Workbench output channel

This extension delegates execution to the mcp-workbench CLI and presents its output inside VS Code.

Features

• Generate Spec from Server — connect to any MCP server and auto-generate a YAML test spec with a guided wizard
• Korean UI — all commands, settings descriptions, and notifications are localised when VS Code is set to Korean (ko)
• Run Current Spec — run the open YAML spec file and see results inline
• Run All Workspace Specs — discover and run all spec files in the workspace
• Update Snapshots — regenerate snapshot baselines for the current spec
• Test Results Tree — collapsible view showing every test and assertion
• Problems Panel Integration — failed assertions appear as diagnostics in the Problems panel
• Output Channel Logs — full run log in the MCP Workbench output panel

Installation

From the VS Code Marketplace

1. Open the Extensions panel (Ctrl+Shift+X / Cmd+Shift+X)
2. Search for MCP Workbench
3. Click Install

Prerequisites

The extension requires the MCP Workbench CLI:

# Primary — scoped package
npm install -g @mcp-workbench/cli

# Alternative — convenience wrapper
npm install -g mcp-workbench-cli

Both install the same mcp-workbench command.

Note: The unscoped mcp-workbench npm package is an unrelated project. Make sure to install one of the two options above.

Quick Start

1. Install the CLI: npm install -g @mcp-workbench/cli
2. Create a spec file (see Spec File Format below)
3. Open the spec file in VS Code
4. Press Cmd+Shift+P → MCP Workbench: Run Current Spec
5. View results in the MCP Workbench panel in the Activity Bar

Usage

Generate a spec from a running server

Click the ✦ button in the MCP Workbench Test Results panel, or use the Command Palette:

MCP Workbench: Generate Spec from Server

A wizard guides you through four steps:

1. Transport — stdio (local process) or streamable-http (HTTP server)
2. Connection — command + args for stdio, or URL for HTTP
3. Depth — shallow (list capabilities only) or deep (also call safe tools)
4. Output file — where to save the generated YAML spec

Run the current spec

Open a *.yaml spec file and click the ▷ button in the editor title bar, or use the Command Palette (Ctrl+Shift+P / Cmd+Shift+P):

MCP Workbench: Run Current Spec

Run all specs in the workspace

MCP Workbench: Run All Workspace Specs

Update snapshots

MCP Workbench: Update Snapshots

Configuration

Spec File Format

The extension recognises files containing apiVersion: mcp-workbench.dev/v0alpha1.

Minimal example:

apiVersion: mcp-workbench.dev/v0alpha1

server:
  transport: stdio
  command: node
  args:
    - dist/server.js

tests:
  - id: tools-list
    act:
      method: tools/list
    assert:
      - kind: status
        equals: success

See the MCP Workbench documentation for the full spec format including snapshots, assertions, and client simulator fixtures.

Troubleshooting

FAQ

Why isn't the npm package named simply mcp-workbench?

The unscoped mcp-workbench name on npm is taken by an unrelated project (an MCP server aggregator). Our CLI is published as @mcp-workbench/cli, with mcp-workbench-cli as a convenience alternative. Both install the same mcp-workbench command.

Roadmap

Development

npm install
npm run build:watch   # incremental build

Press F5 in VS Code to launch the Extension Development Host.

Contributing

Contributions are welcome. Please open an issue or submit a pull request.

For core CLI and spec engine development, see the main MCP Workbench repository.

License

Apache-2.0