The phrase "a very simple tool" is correct and usable in written English.
You can use it when describing a tool that is easy to use or understand, often in a technical or instructional context.
Example: "This software is designed to be a very simple tool for beginners to learn the basics of coding."
Alternatives: "an easy-to-use tool" or "a basic tool."
It's a challenge to produce something good with a very simple tool".
It's a very simple tool, but a versatile one, and I don't know where I'd be without it.
But all can be modeled using a very simple tool: the state model of input devices.
The work contributes not only to our understanding of the underlying mechanisms but also develops a very simple tool for predicting thawing/impregnation phenomena during cold immersion storage.
The optical technique is presented as a very simple tool to optimally devise the internal design of nozzles and then, to control air entrainment.
The Si/modified SiO2/electrolyte structure is a very simple tool for studying ionic adsorption at the modified SiO2/electrolyte interface, where ionic response of ISFET sensors (Ion Sensitive Field Effect Transistor) originates.
They have borrowed, from medicine, what Duflo calls a "very robust and very simple tool": they subject social-policy ideas to randomized control trials, as one would use in testing a drug.
"We want to collect all this fragmented data and deliver to users one very simple tool to capture their lives.
"There are certain things that we'll provide, like very simple tools like a shared folder or the ability to have a conversation around something, but anything that solves this problem in a fundamental way will unify the file world and post-file world," he said.
[UK] Timed perfectly to coincide with the Copenhagen Climate Summit, AlertMe has launched the Swingometer, a very simple visualisation tool that gives an overview of its customers' home energy use.
A very simple annotation tool has been created as a prototype.
