diff --git a/cargo/README.md b/cargo/README.md
new file mode 100644
index 000000000..544536b4e
--- /dev/null
+++ b/cargo/README.md
@@ -0,0 +1,25 @@
+This folder integrates Rust crates.io fetching into Bazel.
+
+After updating dependencies in ../rslib/Cargo.toml, change to this
+folder and run python update.py to update the external Bazel repositories
+to point to the updated deps.
+
+You will need to have cargo-raze 0.6.1 or later installed, which is not
+currently included in this Bazel project. You can install it by installing
+rustup, then running "cargo install cargo-raze".
+
+A couple of crates need extra work to build with Bazel, and are listed
+in raze.toml. For example:
+
+```toml
+[raze.crates.ring.'0.16.15']
+data_attr = "glob([\"src/**\"])"
+```
+
+After updating dependencies, if one of these crates has changed to a
+new version, the version in raze.toml will need to be updated, and
+update.py re-run.
+
+The ../pylib/rsbridge folder has a dependency on pyo3, which is
+special-cases in update.py. If updating the pyo3 version, raze.toml
+and update.py need to be updated as well.
diff --git a/cargo/update.py b/cargo/update.py
index 8a0664546..e4f26b685 100644
--- a/cargo/update.py
+++ b/cargo/update.py
@@ -1,13 +1,9 @@
 #!/usr/bin/env python3
 #
-# Fetches dependencies from ../rslib/Cargo.toml, adds pyo3
-# for rsbridge, runs cargo update, then outputs the dependencies
-# as Bazel targets.
-#
+# See README.md
 
 EXTRA_DEPS = [
-    # when updating, the version number in raze.toml will need updating too
-    'pyo3 = { version = "0.12.0", features = ["extension-module"] }'
+    'pyo3 = { version = "0.12.3", features = ["extension-module"] }'
 ]
 
 import os
diff --git a/pip/README.md b/pip/README.md
index 64d3de558..64d222871 100644
--- a/pip/README.md
+++ b/pip/README.md
@@ -5,8 +5,6 @@ it will miss packages that are required on Windows and vice versa.
 
 So we're stuck manually merging dependencies for now. To update deps:
 
-- comment out the pyaudio line starting with https:// in requirements.txt,
-  as pip-tools can't handle it
 - run 'bazel run update' to update requirements.txt for the current
   platform
 - consult the git diff, and manually merge the changes, undoing the removal