docs: Explain use of auto-provisioning for required plugins

Signed-off-by: Stephen Finucane <[email protected]>

Author: stephenfin

docs/installation.rst

@@ -5,7 +5,7 @@ As tool
 -------
 
 :pypi:`tox` is a CLI tool that needs a Python interpreter (version 3.9 or higher) to run. We recommend either
-:pypi:`pipx` or  :pypi:`uv` to install tox into an isolated environment. This has the added benefit that later you'll
+:pypi:`pipx` or :pypi:`uv` to install tox into an isolated environment. This has the added benefit that later you'll
 be able to upgrade tox without affecting other parts of the system. We provide method for ``pip`` too here but we
 discourage that path if you can:
 

docs/plugins.rst

@@ -6,6 +6,29 @@ For users
 
 Many plugins are available for tox. These includes, but are not limited to, the extensions found on the ``tox-dev`` org on ':gh:`GitHub <tox-dev>`.
 
+Plugins are automatically discovered once from the Python environment that tox itself is installed in. This means that
+if tox is installed in an isolated environment (e.g. when installed using :pypi:`pipx` or :pypi:`uv`), the plugin(s) be
+installed in the same environment. To ensure a plugin is always available, you can include the plugin is listed in
+:ref:`requires`, which will cause tox to auto-provision a new isolated environment with both tox and the plugin(s)
+installed. For example:
+
+.. tab:: TOML
+
+   .. code-block:: toml
+
+        requires = ["tox>=4", "tox-uv>=1"]
+
+.. tab:: INI
+
+   .. code-block:: ini
+
+        [tox]
+        requires =
+            tox>=4
+            tox-uv>=1
+
+For more information, refer to :ref:`the user guide <auto-provisioning>`.
+
 For developers
 --------------
 

docs/user_guide.rst

@@ -382,6 +382,7 @@ you want to do more research, we recommend taking a look at these projects:
 - `Invoke <https://www.pyinvoke.org/>`__ is a general-purpose task execution library, similar to Make. Invoke is far
   more general-purpose than tox but it does not contain the Python testing-specific features that tox specializes in.
 
+.. _auto-provisioning:
 
 Auto-provisioning
 -----------------