From 938d273d4291f242a6718cd4849d55b8ef04b9b7 Mon Sep 17 00:00:00 2001
From: Graham Esau <gesau@hotmail.co.uk>
Date: Tue, 24 Dec 2019 23:20:11 +0000
Subject: [PATCH] Document feature flags

---
 docs/4-features.md | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/docs/4-features.md b/docs/4-features.md
index 11d599a..5ebc637 100644
--- a/docs/4-features.md
+++ b/docs/4-features.md
@@ -4,6 +4,22 @@ title: Feature Flags
 nav_order: 5
 ---
 
-# Feature Flags
+# Feature Flags and Optional Dependencies
 
-Feature flags that can be enabled..
\ No newline at end of file
+Some functionality can be selectively enabled/disabled via [Cargo features](https://doc.rust-lang.org/cargo/reference/manifest.html#the-features-section). These can be enabled when you add Schemars to your crate's cargo.toml, e.g.
+```toml
+[dependencies]
+schemars = { version = "0.6", features = ["chrono"] }
+```
+
+<div class="indented">
+
+### derive_json_schema
+
+Implements `JsonSchema` on Schemars types themselves.
+
+### chrono
+
+Implements `JsonSchema` on all [Chrono](https://github.com/chronotope/chrono) types which are serializable by Serde.
+
+</div>