OpenSpec MCP Server (AI Assistant Plugin)

Welcome! This is a simple bridge (plugin) that connects OpenSpec to your favorite AI coding assistant (like IBM Bob, Codex, or Claude Desktop).

What is this and why do I need it?

When you want your AI to build a new feature, you usually just type it into the chat. But as projects grow, the AI can forget things, get confused, or write messy code.

OpenSpec is a system that solves this. It forces the AI to create a clear "specification" (a plan) before it writes any code. It organizes your plan into neat folders (proposal, design, tasks) so you can review it.

However, your AI doesn't automatically know how to use OpenSpec. That is what this server does! It gives your AI the "tools" it needs to automatically create these folders, list tasks, and mark them as complete as it writes code for you.

How to Connect Your AI

To use this, you need to tell your AI assistant where this server is located. The setup simply depends on which AI assistant you use.

Option 1: Connecting to IBM Bob

If you are using IBM Bob:

1. In the IBM Bob IDE, click the three dots next to the gear icon in the upper right corner of the chat window and select MCP servers.
2. Click Open next to "Global MCPs" to edit your settings file (usually saved at ~/.bob/settings/mcp_settings.json).
3. Add the openspec server to the mcpServers object:

{
  "mcpServers": {
    "openspec": {
      "command": "npx",
      "args": [
        "-y",
        "@igor-olikh/openspec-mcp-server"
      ]
    }
  }
}

1. Save the file and restart IBM Bob!

Option 2: Connecting to Codex

Codex has a built-in user interface to easily add these plugins. You can add it quickly by running this terminal command:

codex mcp add openspec-server npx -y @igor-olikh/openspec-mcp-server

Or, manually through the Codex User Interface:

1. Open the "Connect to a custom MCP" box in Codex.
2. Name: openspec
3. Mode: Leave as STDIO
4. Command to launch: npx
5. Arguments: Click + Add argument twice and paste exactly:
   • First argument: -y
   • Second argument: @igor-olikh/openspec-mcp-server
6. Working directory: Leave this blank! (This allows Codex to dynamically use OpenSpec inside whichever project you currently have open).
7. Save it!

Option 3: Connecting to Claude Desktop App

If you prefer using the Claude Desktop application:

1. Open your Claude configuration file (usually located at ~/Library/Application Support/Claude/claude_desktop_config.json on Mac).
2. Add the openspec server to it:

{
  "mcpServers": {
    "openspec": {
      "command": "npx",
      "args": [
        "-y",
        "@igor-olikh/openspec-mcp-server"
      ]
    }
  }
}

1. Save the file and restart Claude Desktop.

How do I use it?

Once connected, you don't need to do anything technical. You just talk to your AI like normal, but ask it to use OpenSpec!

Example Chat Prompts:

• "Hey Bob, I want to add a dark mode feature to this application. Please use OpenSpec to propose and validate it."
• "What is the OpenSpec status of our current project?"
• "List all the OpenSpec changes we are currently working on."

The AI will automatically use the tools below to handle the rest!

For Developers (Under the Hood)

This server exposes the official @fission-ai/openspec CLI commands as Model Context Protocol (MCP) JSON-RPC tools.

Available AI Tools:

• openspec_init: Starts OpenSpec in a project.
• openspec_new_change: Creates a folder for a new feature proposal.
• openspec_status: Checks how much of the feature is done.
• openspec_validate: Checks if the code matches the plan.
• openspec_archive: Marks the feature as 100% completed.
• openspec_list: Shows all current tasks.
• openspec_show: Reads a specific task.
• openspec_update: Updates OpenSpec rules.
• openspec_instructions: Reads AI instructions for building parts of the plan.
• openspec_read_file: Reads any spec artifact directly by name and file type — much faster than show, no subprocess overhead.
• openspec_refresh_cache: Force-refreshes the cached directory listing if files changed outside OpenSpec tools.

Built-in Prompts:

• openspec_kickoff: A pre-made prompt that steers the AI into a strict spec-driven workflow from the first turn. Automatically injected when supported by the AI assistant.

Development Setup

If you want to modify this server's code:

1. npm install (Installs dependencies)
2. npm run build (Compiles the code)
3. npm run start (Runs the server to test standard input/output)

Recent Changes

• Built-in MCP Prompts: The openspec_kickoff prompt automatically steers your AI into a strict spec-driven workflow from the first turn.
• Direct File Readers with In-Memory Cache: New openspec_read_file tool reads spec artifacts directly via the filesystem, bypassing CLI subprocess overhead. An in-memory cache of the directory structure serves list queries in under 1ms. Cache auto-refreshes after any mutating operation.

Upcoming Features (Planned via OpenSpec)

• Structured JSON Outputs: Replacing raw terminal output with parsed JavaScript objects, preventing the AI from misreading states and reducing hallucinations.
• Smart Error Handling: Coaching the LLM when OpenSpec validations fail (e.g. intercepting terminal errors to output: "Hey, you forgot the 'Tasks' header in design.md").