start command

Start the Data API builder runtime with an existing configuration file.

Syntax

dab start [options]

Quick glance

Head section

-c, --config

Path to config file. Defaults to dab-config.json unless dab-config.<DAB_ENVIRONMENT>.json exists, where DAB_ENVIRONMENT is an environment variable.

Example

dab start \
  --config ./settings/dab-config.json

dab start ^
  --config .\settings\dab-config.json

--LogLevel <level>

Specifies logging level as provided value. For possible values, see Log levels.

Example

dab start \
  --LogLevel Warning

dab start ^
  --LogLevel Warning

--no-https-redirect

Disables automatic HTTP→HTTPS redirection.

Example

dab start \
  --no-https-redirect

dab start ^
  --no-https-redirect

--mcp-stdio

Starts Data API builder as an MCP server that uses standard input and output instead of binding to an HTTP port. In this mode, DAB communicates with an MCP client (such as GitHub Copilot, Visual Studio (VS) Code, or any MCP-compatible AI agent) entirely over stdin and stdout by using the Model Context Protocol. No HTTP server or network port is exposed.

This flag also accepts an optional positional role:<role-name> argument that specifies the DAB permission role under which all MCP tool calls execute. The role must match a name defined in the permissions section of your entity configuration. If omitted, the role defaults to anonymous.

When --mcp-stdio is active, the following behaviors are applied automatically regardless of your config file settings:

• Encoding: Console input/output is forced to UTF-8 without a byte order mark (BOM) for clean JSON-over-standard input/output communication.
• Authentication: The authentication provider is forced to Simulator mode, enabling the specified role without requiring a real JSON Web Token (JWT) or identity provider.
• No HTTP host: DAB doesn't bind to any Transmission Control Protocol (TCP) port. The MCP server runs entirely over stdin/stdout.

Required config

MCP must be enabled in your dab-config.json before using --mcp-stdio:

"runtime": {
  "mcp": {
    "enabled": true,
    "path": "/mcp",
    "dml-tools": {
      "create-record": true,
      "read-records": true,
      "update-record": true,
      "delete-record": true
    }
  }
}

Example

# Default anonymous role
dab start \
  --mcp-stdio \
  --config ./dab-config.json

# Specific role
dab start \
  --mcp-stdio role:authenticated \
  --config ./dab-config.json

# With logging
dab start \
  --mcp-stdio role:api-reader \
  --config ./dab-config.json \
  --LogLevel Information

:: Default anonymous role
dab start ^
  --mcp-stdio ^
  --config .\dab-config.json

:: Specific role
dab start ^
  --mcp-stdio role:authenticated ^
  --config .\dab-config.json

:: With logging
dab start ^
  --mcp-stdio role:api-reader ^
  --config .\dab-config.json ^
  --LogLevel Information

MCP client configuration

Because DAB runs as a subprocess that communicates over standard input and output, your MCP client must launch DAB as a child process and pipe stdin and stdout. A typical MCP client configuration for Visual Studio (VS) Code or a compatible agent looks like:

{
  "servers": {
    "my-database": {
      "type": "stdio",
      "command": "dab",
      "args": [
        "start",
        "--mcp-stdio",
        "role:anonymous",
        "--config",
        "./dab-config.json"
      ]
    }
  }
}

For a complete walkthrough, see standard input and output transport for SQL MCP Server.

--verbose

Sets the logging level to Informational. This is a convenience flag equivalent to --LogLevel Information.

Example

dab start \
  --verbose

dab start ^
  --verbose

--help

Display the help screen.

Example

dab start --help

dab start --help

--version

Display version information.

Example

dab start --version

dab start --version