What timing! I have been making this exact thing myself.

Would you be interested in pull requests making your api simpler? Maybe allow parameters to not have to have shapes? Perhaps allowing a syntax that allows a simple way to shapes in the meta alongside the ability to change the signature for people who don't want to couple too tightly to the library? When I showed mine to my local user group last month, that was one of their biggest requests (that I was in the middle of on mine but would be happy to attempt in yours).

Check my (simpler and more immature) library here https://github.com/steveshogren/deft