When you install ACP, an icon is placed on your desktop labeled ACP Plan Checker. This useful tool provides you a way to check an ACP Observing Plan for validity before submitting it for a run. It will detect many types of errors, including invalid directives, bad coordinate or orbital element formats, missing arguments on directives, etc. It will also detect conflicting directives such as a plan with both #chain and #shutdown.
The Plan Checker does not check all of the errors that are checked at run start by the AcquireImages.js script. The Plan Checker is designed to run on a system that doesn't have ACP installed. However AcquireImages.js by definition is running on a system with ACP, so it can do deeper checking. Be aware that Plan Checker is a good tool for detecting most errors, but you may still find (obscure) errors at the start of a plan. Drag and drop a plan file on to the ACP Plan Checker icon (recommended for ease of use). You can also double-click the icon, in which case you'll see a popup "ease of use" message telling you that you can drag and drop and asking if you want to browse for the file. Clicking Yes will show the file browser where you can select the plan to check.
In any case, shortly thereafter, a Notepad window will appear containing either a list of errors in the plan, or if the plan is error-free, a detailed dump of the plan's observing requests.