diff --git a/site/en/_book.yaml b/site/en/_book.yaml
index f9528a3..bc55891 100644
--- a/site/en/_book.yaml
+++ b/site/en/_book.yaml
@@ -150,6 +150,8 @@
         path: /configure/attributes
       - title: Integrating with C++ rules
         path: /configure/integrate-cpp
+      - title: Implementing toolchain resolution
+        path: /configure/toolchain-resolution
       - title: Code coverage with Bazel
         path: /configure/coverage
       - heading: Optimizing Bazel
diff --git a/site/en/configure/toolchain-resolution.md b/site/en/configure/toolchain-resolution.md
new file mode 100644
index 0000000..2713c21
--- /dev/null
+++ b/site/en/configure/toolchain-resolution.md
@@ -0,0 +1,56 @@
+Project: /_project.yaml
+Book: /_book.yaml
+
+# Toolchain Resolution Implementation Details
+
+{% include "_buttons.html" %}
+
+**Note:** This section is intended for Bazel developers, and is not needed by
+rule authors.
+
+Several SkyFunction classes implement the [toolchain resolution](/extending/toolchains) process:
+
+1.  [`RegisteredToolchainsFunction`](https://github.com/bazelbuild/bazel/blob/master/src/main/java/com/google/devtools/build/lib/skyframe/RegisteredToolchainsFunction.java) and
+    [`RegisteredExecutionPlatformsFunction`](https://github.com/bazelbuild/bazel/blob/master/src/main/java/com/google/devtools/build/lib/skyframe/RegisteredExecutionPlatformsFunction.java)
+    find available toolchains and execution platforms, based on the current
+    configuration and WORKSPACE file.
+
+1.  [`SingleToolchainResolutionFunction`](https://github.com/bazelbuild/bazel/blob/master/src/main/java/com/google/devtools/build/lib/skyframe/SingleToolchainResolutionFunction.java)
+    resolves a single toolchain type for every execution platform. That is, for
+    every execution platform it finds the best registered toolchain to use based
+    on the following criteria:
+
+    1.  Make sure the toolchain and target platform are compatible, by checking
+        the `target_compatible_with` attribute.
+    1.  Make sure the toolchain and execution platform are compatible, by
+        checking the `exec_compatible_with` attribute.
+    1.  If multiple toolchains are left, choose the highest-priority one (the
+        one that was registered first).
+
+1.  [`ToolchainResolutionFunction`](https://github.com/bazelbuild/bazel/blob/master/src/main/java/com/google/devtools/build/lib/skyframe/ToolchainResolutionFunction.java) calls
+    `SingleToolchainResolutionFunction` for each requested toolchain type, and
+    then determines the best execution platform to use.
+
+    1.  First, remove any execution platform that does not have a valid
+        toolchain for each requested toolchain type.
+    2.  If multiple execution platforms are left, choose the highest-priority
+        one (the one that was registered first).
+        1.  If the execution platform is already set by the toolchain
+            transition, it will be selected first as described below.
+
+As discussed in [Toolchains and Configurations](/extending/toolchains#toolchains_and_configurations),
+the dependency from a target to a toolchain uses a special configuration that
+forces the execution platform to be the same for both. Despite the name
+"toolchain transition", this is not implemented as a configuration
+transition, but instead as a special subclass of
+[`ConfiguredTargetKey`](https://github.com/bazelbuild/bazel/blob/master/src/main/java/com/google/devtools/build/lib/skyframe/ConfiguredTargetKey.java), called
+[`ToolchainDependencyConfiguredTargetKey`](https://github.com/bazelbuild/bazel/blob/master/src/main/java/com/google/devtools/build/lib/skyframe/ConfiguredTargetKey.java;bpv=1;bpt=1;l=164?ss=bazel&q=ConfiguredTargetKey&gsn=ToolchainDependencyConfiguredTargetKey&gs=kythe%3A%2F%2Fgithub.com%2Fbazelbuild%2Fbazel%3Flang%3Djava%3Fpath%3Dcom.google.devtools.build.lib.skyframe.ConfiguredTargetKey.ToolchainDependencyConfiguredTargetKey%2336c7e68f8cd5ea0b5a21b3769e63e6b2d489b9ca8c6f79798839e7f40cf2a19e).
+In addition to the other data in `ConfiguredTargetKey`, this subclass also holds
+the label of the execution platform. When `ToolchainResolutionFunction` is
+considering which execution platform to use, if the forced execution platform
+from the `ToolchainDependencyConfiguredTargetKey` is valid, it will be used even
+if it is not the highest-priority.
+
+**Note:** If the forced execution platform is not valid (because there are no
+valid toolchains, or because of execution constraints from the rule or target),
+then the highest-priority valid execution platform will be used instead.
diff --git a/site/en/docs/_index.yaml b/site/en/docs/_index.yaml
index aaada84..2585586 100644
--- a/site/en/docs/_index.yaml
+++ b/site/en/docs/_index.yaml
@@ -111,6 +111,8 @@
       path: /configure/attributes
     - heading: Integrating with C++ rules
       path: /configure/integrate-cpp
+    - heading: Implementing toolchain resolution
+      path: /configure/toolchain-resolution
     - heading: Code coverage with Bazel
       path: /configure/coverage
     - heading: "Optimizing Bazel: Best practices"
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/toolchains/README.md b/src/main/java/com/google/devtools/build/lib/skyframe/toolchains/README.md
deleted file mode 100644
index 47f1f12..0000000
--- a/src/main/java/com/google/devtools/build/lib/skyframe/toolchains/README.md
+++ /dev/null
@@ -1,57 +0,0 @@
-# Toolchain Resolution Implementation Details
-
-Several SkyFunction classes implement the [toolchain resolution] process:
-
-1.  [`RegisteredToolchainsFunction`] and
-    [`RegisteredExecutionPlatformsFunction`] find available toolchains and
-    execution platforms, based on the current configuration and WORKSPACE file.
-
-1.  [`SingleToolchainResolutionFunction`] resolves a single toolchain type for
-    every execution platform. That is, for every execution platform it finds the
-    best registered toolchain to use based on the following criteria:
-
-    1.  Make sure the toolchain and target platform are compatible, by checking
-        the `target_compatible_with` attribute.
-    1.  Make sure the toolchain and execution platform are compatible, by
-        checking the `exec_compatible_with` attribute.
-    1.  If multiple toolchains are left, choose the highest-priority one (the
-        one that was registered first).
-
-1.  [`ToolchainResolutionFunction`] calls `SingleToolchainResolutionFunction`
-    for each requested toolchain type, and then determines the best execution
-    platform to use.
-
-    1.  First, remove any execution platform that does not have a valid
-        toolchain for each requested toolchain type.
-    2.  If multiple execution platforms are left, choose the highest-priority
-        one (the one that was registered first).
-        1.  If the execution platform is already set by the toolchain
-            transition, it will be selected first as described below.
-
-As discussed in [Toolchains and Configurations][toolchains_and_configurations],
-the dependency from a target to a toolchain uses a special configuration that
-forces the execution platform to be the same for both. Despite the name
-"toolchain transition", this is not implemented as a configuration transition,
-but instead as a special subclass of [`ConfiguredTargetKey`], called
-[`ToolchainDependencyConfiguredTargetKey`].  In addition to the other data in
-`ConfiguredTargetKey`, this subclass also holds the label of the execution
-platform. When `ToolchainResolutionFunction` is considering which execution
-platform to use, if the forced execution platform from the
-`ToolchainDependencyConfiguredTargetKey` is valid, it will be used even if it is
-not the highest-priority.
-
-**Note:** If the forced execution platform is not valid (because there are no
-valid toolchains, or because of execution constraints from the rule or target),
-then the highest-priority valid execution platform will be used instead.
-
-**TODO:** Update this to discuss execution groups.
-
-[toolchain resolution]: https://bazel.build/extending/toolchains
-[toolchains_and_configurations]: https://bazel.build/extending/toolchains#toolchains_and_configurations
-[`ConfiguredTargetKey`]: https://cs.opensource.google/bazel/bazel/+/master:src/main/java/com/google/devtools/build/lib/skyframe/ConfiguredTargetKey.java
-[`RegisteredExecutionPlatformsFunction`]: https://cs.opensource.google/bazel/bazel/+/master:src/main/java/com/google/devtools/build/lib/skyframe/toolchains/RegisteredExecutionPlatformsFunction.java
-[`RegisteredToolchainsFunction`]: https://cs.opensource.google/bazel/bazel/+/master:src/main/java/com/google/devtools/build/lib/skyframe/toolchains/RegisteredToolchainsFunction.java
-[`SingleToolchainResolutionFunction`]: https://cs.opensource.google/bazel/bazel/+/master:src/main/java/com/google/devtools/build/lib/skyframe/toolchains/SingleToolchainResolutionFunction.java;
-[`ToolchainDependencyConfiguredTargetKey`]: https://cs.opensource.google/bazel/bazel/+/master:src/main/java/com/google/devtools/build/lib/skyframe/ConfiguredTargetKey.java?q=symbol%3A%5Cbcom.google.devtools.build.lib.skyframe.ConfiguredTargetKey.ToolchainDependencyConfiguredTargetKey%5Cb%20case%3Ayes
-[`ToolchainResolutionFunction`]: https://cs.opensource.google/bazel/bazel/+/master:src/main/java/com/google/devtools/build/lib/skyframe/toolchains/ToolchainResolutionFunction.java
-