Many of our database commands do not have IDL files, causing the following problems:

• not knowing which fields a command takes or returns, or where to find that information

• not knowing the type of a command's input/return values, or where to find that information. For example, which fields in TopologyCoordinator::prepareStatusResponse are guaranteed to exist and which are optional?

• not having documentation for a command, or its input/return values, or knowing where to find it. For example, it takes time to figure out what code like this is for without some prior knowledge:

function getWatchDogCheckGeneration(node) {
    const result = node.adminCommand({"serverStatus": 1});
    assert.commandWorked(result);
    return result.watchdog.checkGeneration;
}

Finally, with SERVER-103950, this information could be presented in our editor while writing jstests, eliminating the need to search through the repository.