JustIn Code: AI Code Agent – Extension

JustIn Code is a VS Code extension that lets you chat with an AI assistant inside VS Code for help with files, code, commands, MCP tools, and web search.

What is it?

• You open it from the Activity Bar, Secondary Side Bar, or Command Palette.
• You type requests in normal language.
• It uses the AI model you configure in justincode.json.
• Web search, MCP servers, and skills are optional extras.
• It shares the same core engine and config as the justincode terminal app.

Requirements

• VS Code 1.105.0 or newer
• Node.js 20 or newer
• An API key for an AI model provider
• Optional: a web search API key if you want live web results

Install

Install from the VS Code Marketplace (or install the .vsix package).

After installing, open the extension with any of these commands:

• JustIn Code: Open in Primary Editor
• JustIn Code: Open in Primary Side Bar
• JustIn Code: Open in Secondary Side Bar

You can also click the JustIn Code Activity Bar icon.

First-time setup

Open the settings file with:

• JustIn Code: Open Settings (justincode.json)

The first time you run JustIn Code, it creates justincode.json if missing. Usually:

• Windows: C:\Users\YOUR_NAME\.config\justincode\justincode.json
• macOS/Linux: ~/.config/justincode/justincode.json

Set up justincode.json

Open the existing justincode.json file and change only the values you need. Do not delete the rest of the file.

Add your model key

Choose the model you want in models.selected, then paste your key into the matching provider apiKey.

Example:

"models": {
  "selected": "openai/gpt-4o-mini",
  "providers": {
    "openai": {
      "options": {
        "baseURL": "https://api.openai.com/v1",
        "apiKey": "PASTE_YOUR_OPENAI_KEY_HERE"
      },
      "models": {
        "gpt-5.2": {
          "name": "gpt-5.2"
        },
        "gpt-4o-mini": {
          "name": "gpt-4o-mini"
        }
      }
    }
  }
}

This follows the same structure the app already uses in justincode.json.

If you use another provider, add your key to that provider and set selected to provider/model. Keep the rest of the JSON structure as it is.

Add your web search key

Web search is optional. If you want it, set the provider name in webSearch.selected and paste the API key for that provider.

Example:

"webSearch": {
  "selected": "tavily",
  "providers": {
    "tavily": {
      "apiKey": "PASTE_YOUR_TAVILY_KEY_HERE"
    }
  }
}

Add MCP servers

MCP servers give the agent extra tools.

Example using the k8s-port-forward MCP server:

"mcp": {
  "enabled": true,
  "servers": {
    "k8s-port-forward": {
      "command": "npx",
      "args": ["-y", "k8s-port-forward-mcp@latest"],
      "env": {},
      "disabled": false
    }
  }
}

Check the MCP server's documentation for its prerequisites (tools, auth, environment).

After saving settings, start a new chat session (or otherwise reload MCP) so the agent loads the server. Then you can ask the agent to use its tools.

Add skills

Skills are small instruction files that teach the agent a specific job or workflow.

1. Create a folder inside one of these directories: ~/.agents/skills, ~/.justincode/skills, or .justincode/skills
2. Inside that folder, create a file named SKILL.md
3. Add the skill name to skills.active

Example skills config:

"skills": {
  "enabled": true,
  "directories": [
    "~/.agents/skills",
    "~/.justincode/skills",
    ".justincode/skills"
  ],
  "active": ["My Skill"]
}

Useful extension commands

• JustIn Code: New Session
• JustIn Code: Change Mode
• JustIn Code: Change Model
• JustIn Code: Open Settings (justincode.json)
• JustIn Code: Open in Terminal

Uninstall

Uninstall the extension from VS Code Extensions view.

If you also want to remove your personal settings, delete the justincode.json file after uninstalling.