When I was more active in LaTeX and Metapost (~10 years ago) I could not find a way to directly use Metapost in LaTeX. There were few tutorials on how to use it within ConTeXt, but for using it with LaTeX you had to make the .mp file separate, compile it into .ps or .pdf and then add the .ps (for latex → dvi → ps) or .pdf (for pdflatex → pdf) using the graphix package.
I am currently seeing many questions related to TikZ, and most examples use TikZ within LaTeX.
So. Are there current tools to use the Metapost language within LaTeX without using a separate source and a separate compilation?