diff --git a/docs/BUILD.gn b/docs/BUILD.gn
index 5bc0f00..f9d371f 100644
--- a/docs/BUILD.gn
+++ b/docs/BUILD.gn
@@ -39,6 +39,7 @@
     ":core_docs",
     ":target_docs",
     "$dir_pw_assert:docs",
+    "$dir_pw_assert_basic:docs",
     "$dir_pw_bloat:docs",
     "$dir_pw_boot_armv7m:docs",
     "$dir_pw_build:docs",
diff --git a/pw_assert/docs.rst b/pw_assert/docs.rst
index 44ed397..c181416 100644
--- a/pw_assert/docs.rst
+++ b/pw_assert/docs.rst
@@ -4,17 +4,49 @@
 
 .. highlight:: cpp
 
----------
+=========
 pw_assert
----------
+=========
+
+--------
+Overview
+--------
 Pigweed's assert module provides facilities for applications to check
-preconditions.  The module is split into two components:
+preconditions. The module is split into two components:
 
 1. The facade (this module) which is only a macro interface layer
 2. The backend, provided elsewhere, that implements the low level checks
 
-Basic usage example
--------------------
+All behaviour is controlled by the backend.
+
+The ``pw_assert`` public API provides three classes of macros:
+
++-----------------------------------------+--------------------------------+
+| PW_CRASH(format, ...)                   | Trigger a crash with a message |
++-----------------------------------------+--------------------------------+
+| PW_CHECK(condition[, format, ...])      | Assert a condition, optionally |
+|                                         | with a message                 |
++-----------------------------------------+--------------------------------+
+| PW_CHECK_<type>_<cmp>(a, b[, fmt, ...]) | Assert that the expression     |
+|                                         | ``a <cmp> b`` is true,         |
+|                                         | optionally with a message.     |
++-----------------------------------------+--------------------------------+
+
+.. tip::
+  All of the assert macros optionally support a message with additional
+  arguments, to assist in debugging when an assert triggers:
+
+  .. code-block:: cpp
+
+    PW_CHECK_INT_LE(ItemCount(), 100);
+    PW_CHECK_INT_LE(ItemCount(), 100, "System state: %s", GetStateStr());
+
+Compatibility
+-------------
+The facade is compatible with C and C++.
+
+Example
+-------
 
 .. code-block:: cpp
 
@@ -23,5 +55,141 @@
   int main() {
     bool sensor_running = StartSensor(&msg);
     PW_CHECK(sensor_running, "Sensor failed to start; code: %s", msg);
+
+    int temperature_c = ReadSensorCelcius();
+    PW_CHECK_INT_LE(temperature_c, 100,
+                    "System is way out of heat spec; state=%s",
+                    ReadSensorStateString());
   }
 
+
+---------------------------
+Assert facade API reference
+---------------------------
+
+The below functions describe the assert API functions that applications should
+invoke to assert.
+
+.. cpp:function:: PW_CRASH(format, ...)
+
+  Trigger a crash with a message. Replaces LOG_FATAL() in other systems. Can
+  include a message with format arguments; for example:
+
+  .. code-block:: cpp
+
+    PW_CRASH("Unexpected: frobnitz in state: %s", frobnitz_state);
+
+  Note: ``PW_CRASH`` is the equivalent of ``LOG_FATAL`` in other systems, where
+  a device crash is triggered with a message. In Pigweed, logging and
+  crashing/asserting are separated. There is a ``LOG_CRITICAL`` level in the
+  logging module, but it does not have side effects; for ``LOG_FATAL``, instead
+  use this macro (``PW_CRASH``).
+
+.. cpp:function:: PW_CHECK(condition)
+.. cpp:function:: PW_CHECK(condition, format, ...)
+
+  Assert that a condition is true, optionally including a message with
+  arguments to report if the codition is false.
+
+  .. code-block:: cpp
+
+    PW_CHECK(StartTurbines());
+    PW_CHECK(StartWarpDrive(), "Oddly warp drive couldn't start; ruh-roh!");
+
+.. cpp:function:: PW_CHECK_TYPE_OP(a, b)
+.. cpp:function:: PW_CHECK_TYPE_OP(a, b, format, ...)
+
+  Asserts that ``a OP b`` is true, where ``a`` and ``b`` are converted to
+  ``TYPE``; with ``OP`` and ``TYPE`` described below.
+
+  If present, the optional format message is reported on failure. Depending on
+  the backend, values of ``a`` and ``b`` will also be reported.
+
+  Example, with no message:
+
+  .. code-block:: cpp
+
+    PW_CHECK_INT_LE(CurrentTemperature(), 100);
+    PW_CHECK_INT_LE(ItemCount(), 100);
+
+  Example, with an included message and arguments:
+
+  .. code-block:: cpp
+
+    PW_CHECK_FLOAT_GE(BatteryVoltage(), 3.2, "System state=%s", SysState());
+
+  Below is the full list of binary comparison assert macros, along with the
+  type specifier. The specifier is irrelevant to application authors but is
+  needed for backend implementers.
+
+  +-------------------+--------------+-----------+-----------------------+
+  | Macro             | a, b type    | condition | a, b format specifier |
+  +-------------------+--------------+-----------+-----------------------+
+  | PW_CHECK_INT_LE   | int          | a <= b    | %d                    |
+  +-------------------+--------------+-----------+-----------------------+
+  | PW_CHECK_INT_LT   | int          | a <  b    | %d                    |
+  +-------------------+--------------+-----------+-----------------------+
+  | PW_CHECK_INT_GE   | int          | a >= b    | %d                    |
+  +-------------------+--------------+-----------+-----------------------+
+  | PW_CHECK_INT_GT   | int          | a >  b    | %d                    |
+  +-------------------+--------------+-----------+-----------------------+
+  | PW_CHECK_INT_EQ   | int          | a == b    | %d                    |
+  +-------------------+--------------+-----------+-----------------------+
+  | PW_CHECK_UINT_LE  | unsigned int | a <= b    | %u                    |
+  +-------------------+--------------+-----------+-----------------------+
+  | PW_CHECK_UINT_LT  | unsigned int | a <  b    | %u                    |
+  +-------------------+--------------+-----------+-----------------------+
+  | PW_CHECK_UINT_GE  | unsigned int | a >= b    | %u                    |
+  +-------------------+--------------+-----------+-----------------------+
+  | PW_CHECK_UINT_GT  | unsigned int | a >  b    | %u                    |
+  +-------------------+--------------+-----------+-----------------------+
+  | PW_CHECK_UINT_EQ  | unsigned int | a == b    | %u                    |
+  +-------------------+--------------+-----------+-----------------------+
+  | PW_CHECK_FLOAT_LE | float        | a <= b    | %f                    |
+  +-------------------+--------------+-----------+-----------------------+
+  | PW_CHECK_FLOAT_LT | float        | a <  b    | %f                    |
+  +-------------------+--------------+-----------+-----------------------+
+  | PW_CHECK_FLOAT_GE | float        | a >= b    | %f                    |
+  +-------------------+--------------+-----------+-----------------------+
+  | PW_CHECK_FLOAT_GT | float        | a >  b    | %f                    |
+  +-------------------+--------------+-----------+-----------------------+
+  | PW_CHECK_FLOAT_EQ | float        | a == b    | %f                    |
+  +-------------------+--------------+-----------+-----------------------+
+
+----------------------------
+Assert backend API reference
+----------------------------
+
+The backend controls what to do in the case of an assertion failure. In the
+most basic cases, the backend could display the assertion failure on something
+like sys_io and halt in a while loop waiting for a debugger. In other cases,
+the backend could store crash details like the current thread's stack to flash.
+
+This module does not provide a backend; see ``pw_assert_basic`` for a basic
+implementation (which we do not advise using in production).
+
+Here are the macros the backend must provide:
+
+.. cpp:function:: PW_HANDLE_CRASH(message, ...)
+
+  The backend should trigger a system crash or halt, and if possible, deliver
+  the specified message and arguments to the user or developer.
+
+.. cpp:function:: PW_HANDLE_ASSERT_FAILURE(condition_str, message, ...)
+
+  This macro is invoked from ``PW_CHECK`` if condition is false.  The
+  application should crash with the given message and specified format
+  arguments, and may optionally include the stringified condition provided in
+  ``condition_str``.
+
+.. cpp:function:: PW_HANDLE_ASSERT_BINARY_COMPARE_FAILURE( \
+    a_str, a_val, op_str, b_str, b_val, type_fmt, message, ...)
+
+  This macro is invoked from the ``PW_CHECK_*_*`` macros if the condition
+  ``a_val op b_val`` is false. The facade API macros have already evaluated and
+  stringified the arguments, so the backend is free to report the details as
+  needed.
+
+  The backend is expected to report the failure to the user or developer in a
+  useful way, potentially capturing the string and values of the binary
+  comparison operands.
diff --git a/pw_assert_basic/BUILD.gn b/pw_assert_basic/BUILD.gn
index 9b39a97..091a095 100644
--- a/pw_assert_basic/BUILD.gn
+++ b/pw_assert_basic/BUILD.gn
@@ -12,6 +12,8 @@
 # License for the specific language governing permissions and limitations under
 # the License.
 
+import("$dir_pw_docgen/docs.gni")
+
 config("default_config") {
   include_dirs = [ "public" ]
 }
@@ -43,3 +45,7 @@
   public = [ "public/pw_assert_basic/assert_basic.h" ]
   sources = public + [ "assert_basic.cc" ]
 }
+
+pw_doc_group("docs") {
+  sources = [ "docs.rst" ]
+}
diff --git a/pw_assert_basic/docs.rst b/pw_assert_basic/docs.rst
new file mode 100644
index 0000000..c930b79
--- /dev/null
+++ b/pw_assert_basic/docs.rst
@@ -0,0 +1,15 @@
+.. _chapter-pw-assert-basic:
+
+.. default-domain:: cpp
+
+.. highlight:: cpp
+
+===============
+pw_assert_basic
+===============
+
+--------
+Overview
+--------
+This is a simple assert backend to complement the ``pw_assert`` facade.
+