diff --git a/src/derive_support.rs b/src/derive_support.rs
index 100b8ef..024eb94 100644
--- a/src/derive_support.rs
+++ b/src/derive_support.rs
@@ -1,9 +1,13 @@
+//! This module contains auxilary functions which one might find useful for
+//! generating implementations of host related functionality like `Externals`.
+
 use nan_preserving_float::{F32, F64};
 use {RuntimeValue, Trap, ValueType};
 
 /// A trait that represents a value that can be directly coerced to one of
 /// wasm base value types.
 pub trait IntoWasmValue {
+    /// The value type into which the self type is converted.
     const VALUE_TYPE: ValueType;
     /// Perform the conversion.
     fn into_wasm_value(self) -> RuntimeValue;
@@ -28,8 +32,15 @@ impl_convertible_to_wasm!(u64, I64, as i64);
 impl_convertible_to_wasm!(F32, F32);
 impl_convertible_to_wasm!(F64, F64);
 
+/// A trait that represents a value that can be returned from a function.
+///
+/// Basically it is superset of `IntoWasmValue` types, adding the ability to return
+/// the unit value (i.e. `()`) and return a value that signals a trap.
 pub trait IntoWasmResult {
+    /// The value type into which the self type is converted or `None` in case
+    /// of the unit value (aka `()` aka `void`).
     const VALUE_TYPE: Option<ValueType>;
+    /// Perform the conversion.
     fn into_wasm_result(self) -> Result<Option<RuntimeValue>, Trap>;
 }