CodeCompanion Integration

Add MCP capabilities to CodeCompanion.nvim by adding it as an extension.

Features

• Access MCP tools via the @mcp tool in the chat buffer.
• Utilize MCP resources as context variables using the # prefix (e.g., #resource_name).
• Execute MCP prompts directly using /mcp:prompt_name slash commands.
• Supports 🖼 images as shown in the demo.
• Receive real-time updates in CodeCompanion when MCP servers change.

MCP Hub Extension

Register MCP Hub as an extension in your CodeCompanion configuration:

require("codecompanion").setup({
  extensions = {
    mcphub = {
      callback = "mcphub.extensions.codecompanion",
      opts = {
        show_result_in_chat = true,  -- Show mcp tool results in chat
        make_vars = true,            -- Convert resources to #variables
        make_slash_commands = true,  -- Add prompts as /slash commands
      }
    }
  }
})

Usage

Once configured, you can interact with MCP Hub within the CodeCompanion chat buffer:

• Tool Access: Type @mcp to add available MCP servers to the system prompt, enabling the LLM to use registered MCP tools.
• Resources as Variables: If make_vars = true, MCP resources become available as variables prefixed with #. You can include these in your prompts (e.g., Summarize the issues in #mcp:lsp:get_diagnostics):

Example: Accessing LSP diagnostics:

Prompts as Slash Commands: If make_slash_commands = true, MCP prompts are available as slash commands (e.g., /mcp:prompt_name). Arguments are handled via vim.ui.input.

Example: Using an MCP prompt via slash command:

Auto-Approval

By default, whenever codecompanion calls use_mcp_tool or access_mcp_resource tool, it shows a confirm dialog with tool name, server name and arguments.

Global Auto-Approval

You can set auto_approve to true to automatically approve all MCP tool calls without user confirmation:

require("mcphub").setup({
    -- This sets vim.g.mcphub_auto_approve to true by default (can also be toggled from the HUB UI with `ga`)
    auto_approve = true, 
})

This also sets vim.g.mcphub_auto_approve variable to true. You can also toggle this option in the MCP Hub UI with ga keymap. You can see the current auto approval status in the Hub UI.

Fine-Grained Auto-Approval

For more control, configure auto-approval per server or per tool in your servers.json:

{
    "mcpServers": {
        "trusted-server": {
            "command": "npx",
            "args": ["trusted-mcp-server"],
            "autoApprove": true  // Auto-approve all tools on this server
        },
        "partially-trusted": {
            "command": "npx", 
            "args": ["some-mcp-server"],
            "autoApprove": ["read_file", "list_files"]  // Only auto-approve specific tools
        }
    }
}

You can also toggle auto-approval from the Hub UI:

• Press a on a server line to toggle auto-approval for all tools on that server
• Press a on an individual tool to toggle auto-approval for just that tool
• Resources are always auto-approved (no configuration needed)

Function-Based Auto-Approval

For maximum control, provide a function that decides approval based on the specific tool call:

require("mcphub").setup({
    auto_approve = function(params)
        -- Respect CodeCompanion's auto tool mode when enabled
        if vim.g.codecompanion_auto_tool_mode == true then
            return true -- Auto approve when CodeCompanion auto-tool mode is on
        end
        
        -- Auto-approve GitHub issue reading
        if params.server_name == "github" and params.tool_name == "get_issue" then
            return true -- Auto approve
        end
        
        -- Block access to private repos
        if params.arguments.repo == "private" then
            return "You can't access my private repo" -- Error message
        end
        
        -- Auto-approve safe file operations in current project
        if params.tool_name == "read_file" then
            local path = params.arguments.path or ""
            if path:match("^" .. vim.fn.getcwd()) then
                return true -- Auto approve
            end
        end
        
        -- Check if tool is configured for auto-approval in servers.json
        if params.is_auto_approved_in_server then
            return true -- Respect servers.json configuration
        end
        
        return false -- Show confirmation prompt
    end,
})

Parameters available in the function:

• params.server_name - Name of the MCP server
• params.tool_name - Name of the tool being called (nil for resources)
• params.arguments - Table of arguments passed to the tool
• params.action - Either "use_mcp_tool" or "access_mcp_resource"
• params.uri - Resource URI (for resource access)
• params.is_auto_approved_in_server - Boolean indicating if tool is configured for auto-approval in servers.json

Return values:

• true - Auto-approve the call
• false - Show confirmation prompt
• string - Deny with error message
• nil - Show confirmation prompt (same as false)

Auto-Approval Priority

The system checks auto-approval in this order:

1. Function: Custom auto_approve function (if provided)
2. Server-specific: autoApprove field in server config
3. Default: Show confirmation dialog