Good ways to contribute

stubtest is a tool that comes bundled with mypy. It compares stubs to what it can deduce from importing and introspecting the library at runtime.

$ pip install mypy
# to find potential issues with the module sys
$ stubtest --custom-typeshed-dir ~/your_copy_of/typeshed sys --concise

We maintain a list of existing stubtest errors on the standard library and third party stubs, that we're looking to either fix or to add a comment explaining why stubtest should be ignored:
Allowlist of errors for the stdlib
Example of allowlist for a third party stub

These lists of existing errors do not include things that are missing entirely from the stubs, so running stubtest yourself (without --ignore-missing-stub) can be a good way to identify places where stubs are missing definitions entirely.

If you have an idea, you could even teach stubtest new tricks to find issues, like #3968

mypy has a lot of different flags that could help identify improvements. For instance, I recommend using the following patch and re-running the test to find places where typeshed stubs are missing annotations:

diff --git a/tests/mypy_test.py b/tests/mypy_test.py
index f32da57f..e94e5a29 100755
--- a/tests/mypy_test.py
+++ b/tests/mypy_test.py
@@ -136,6 +136,8 @@ def main():
             flags.append('--no-implicit-optional')
             flags.append('--disallow-any-generics')
             flags.append('--disallow-subclassing-any')
+            flags.append('--disallow-incomplete-defs')
+            flags.append('--warn-incomplete-stub')
             if args.warn_unused_ignores:
                 flags.append('--warn-unused-ignores')
             if args.platform:

Similarly, we run checks against some stubs with looser pyright settings. By running with a more strict pyright setting, we can find issues.

We've had requests for stubs for at least the following libraries:

zxcvbn
pyspark
psutil
pymongo
setuptools
python-future
pyzmq
pynput
z3
pony

Take a look at CONTRIBUTING.md for more guidance, but note that for larger libraries we accept partial / incomplete stubs. Note that you should check whether the library already provides (or is interested in providing) inline types or in-package stubs — types are typically best maintained by library authors.

As mentioned in point 3, we accept partial / incomplete stubs. As recommended by https://github.com/python/typeshed/blob/master/CONTRIBUTING.md#incomplete-stubs, these are marked with a comment that says # incomplete. They're waiting for you to complete them!

Another thing to search for is module level def __getattr__. stubtest is pretty good with helping point out ways to complete stubs.

We currently specify a specific version of a third party package our stubs are meant to describe in each stub's METADATA.toml file. Changing this version to the latest and seeing what stubtest has to say is a great way to help keep type information up to date.

Also note that several of the previous points apply, in particular, fixing existing errors in the stubtest allowlist for a third party package (allowlist can be found in the @tests directory)