Code Mode

Overview

Code Mode is useful when you connect many MCP servers and do not want every model request to include every tool definition. Instead of exposing each tool directly, ModRouter exposes a compact set of meta-tools that let the model discover tool definitions and execute tool orchestration code in a sandbox. Use Code Mode when:

You have several MCP servers connected.
Workflows require multiple tool calls.
Tool definitions take too much context.
Intermediate tool results do not all need to be sent back to the model.

For simple one-tool or two-tool use cases, classic MCP tool calling is usually easier.

How It Works

Code Mode exposes meta-tools such as:

Tool	Purpose
`listToolFiles`	Discover available tool files
`readToolFile`	Load tool signatures on demand
`getToolDocs`	Read detailed docs for a tool
`executeToolCode`	Execute sandboxed code that calls MCP tools

The model reads only the tool definitions it needs, writes orchestration code, and receives a compact result.

Enable Code Mode

Enable Code Mode per MCP client:

{
  "mcp": {
    "client_configs": [
      {
        "name": "web_search",
        "connection_type": "http",
        "connection_string": "https://mcp.example.com/mcp",
        "tools_to_execute": ["*"],
        "is_code_mode_client": true
      }
    ],
    "tool_manager_config": {
      "code_mode_binding_level": "tool"
    }
  }
}

Send a Request

export MODROUTER_BASE_URL="https://api.modrouter.online"
export MODROUTER_API_KEY="<your-modrouter-virtual-key>"

curl --location "https://api.modrouter.online/v1/chat/completions" \
  --header "Authorization: Bearer ${MODROUTER_API_KEY}" \
  --header 'Content-Type: application/json' \
  --data '{
    "model": "openai/gpt-4o-mini",
    "messages": [
      {
        "role": "user",
        "content": "Search for the latest release notes and save a concise summary."
      }
    ],
    "tool_choice": "auto"
  }'

Go SDK

mcpConfig := &schemas.MCPConfig{
    ClientConfigs: []schemas.MCPClientConfig{
        {
            Name:             "web_search",
            ConnectionType:   schemas.MCPConnectionTypeHTTP,
            ConnectionString: modrouter.Ptr("https://mcp.example.com/mcp"),
            ToolsToExecute:   []string{"*"},
            IsCodeModeClient: modrouter.Ptr(true),
        },
    },
    ToolManagerConfig: &schemas.MCPToolManagerConfig{
        CodeModeBindingLevel: "tool",
    },
}

Practical Guidance

Enable Code Mode for broad tool surfaces such as search, documents, CRM, databases, and internal APIs. Keep small utility servers in classic MCP mode when direct tool calling is clearer.

CLI Agents & Editors

MCP Gateway

Overview

How It Works

Enable Code Mode

Send a Request

Go SDK

Practical Guidance

​Overview

​How It Works

​Enable Code Mode

​Send a Request

​Go SDK

​Practical Guidance

Overview

How It Works

Enable Code Mode

Send a Request

Go SDK

Practical Guidance