bin-annot
Like ocaml-annot, but for binary annotation files (cmt).
If you compile your OCaml code with the -bin-annot option, bin-annot -type l c file.cmt
can tell what's the type of the thing at line l, column c of file.ml.
Editor integration
It is the same command line than ocaml-annot so that editor configuration should stay the same.
Build
You need findlib aka ocamlfind, and ocaml-compiler-libs (both available on opam).
Then:
make && make install