Some minor changes and additional documentation.

src/main/scala/gs/config/AuditedConfiguration.scala

@@ -1,5 +1,6 @@
 package gs.config
 
+import cats.data.NonEmptyList
 import cats.effect.Sync
 import cats.syntax.all.*
 import gs.config.audit.ConfigManifest
@@ -8,8 +9,16 @@ import gs.config.source.ConfigSource
 import gs.config.source.EnvironmentConfigSource
 import gs.config.source.MemoryConfigSource
 
+/** Implementation of [[gs.config.Configuration]] that tracks every call to
+  * `getValue` and reports on whether the query succeeded or failed.
+  *
+  * @param sources
+  *   List of sources to use, in order, when resolving keys.
+  * @param manifest
+  *   The manifest used to audit configuration loaded by this class.
+  */
 final class AuditedConfiguration[F[_]: Sync](
-  val sources: List[ConfigSource[F]],
+  val sources: NonEmptyList[ConfigSource[F]],
   val manifest: ConfigManifest[F]
 ) extends BaseConfiguration[F]:
   import AuditedConfiguration.Acc
@@ -70,8 +79,17 @@ final class AuditedConfiguration[F[_]: Sync](
 
 object AuditedConfiguration:
 
-  def forSources[F[_]: Sync](sources: List[ConfigSource[F]])
-    : F[Configuration[F]] =
+  /** Instantiate a new [[AuditedConfiguration]] based on the given list of
+    * sources.
+    *
+    * @param sources
+    *   The list of [[ConfigSource]] backing this configuration.
+    * @return
+    *   The new [[Configuration]] instance.
+    */
+  def forSources[F[_]: Sync](
+    sources: NonEmptyList[ConfigSource[F]]
+  ): F[Configuration[F]] =
     ConfigManifest
       .standard[F]
       .map(manifest =>
@@ -81,25 +99,32 @@ object AuditedConfiguration:
         )
       )
 
-  def builder[F[_]: Sync]: Builder[F] = Builder[F](Vector.empty)
+  def forSource[F[_]: Sync](source: ConfigSource[F]): Builder[F] =
+    Builder[F](NonEmptyList.of(source))
 
-  case class Builder[F[_]: Sync](sources: Vector[ConfigSource[F]]):
+  def forEnvironmentSource[F[_]: Sync]: Builder[F] =
+    Builder[F](NonEmptyList.of(new EnvironmentConfigSource[F]))
+
+  def forMemorySource[F[_]: Sync](configs: Map[String, String]): Builder[F] =
+    Builder[F](NonEmptyList.of(new MemoryConfigSource[F](configs)))
+
+  case class Builder[F[_]: Sync](sources: NonEmptyList[ConfigSource[F]]):
 
     def withEnvironmentSource(): Builder[F] =
-      copy(sources = this.sources.appended(new EnvironmentConfigSource[F]))
+      copy(sources = this.sources.append(new EnvironmentConfigSource[F]))
 
     def withMemorySource(configs: Map[String, String]): Builder[F] =
-      copy(sources = this.sources.appended(new MemoryConfigSource[F](configs)))
+      copy(sources = this.sources.append(new MemoryConfigSource[F](configs)))
 
     def withSource(source: ConfigSource[F]): Builder[F] =
-      copy(sources = this.sources.appended(source))
+      copy(sources = this.sources.append(source))
 
     def build(): F[Configuration[F]] =
       ConfigManifest
         .standard[F]
         .map(manifest =>
           new AuditedConfiguration[F](
-            sources = sources.toList,
+            sources = sources,
             manifest = manifest
           )
         )

src/main/scala/gs/config/Configuration.scala

@@ -1,21 +1,33 @@
 package gs.config
 
 import cats.effect.Sync
+import gs.config.source.ConfigSource
 
-/** Interface for loading configuration.
+/** Interface for loading configuration. This type should not be used for any
+  * sensitive configuration such as secrets or private keys.
   */
 trait Configuration[F[_]]:
+  /** Retrieve a value based on some key.
+    *
+    * @param key
+    *   The key that identifies the piece of configuration to retrieve.
+    * @return
+    *   The value, or an error if no value is present.
+    */
   def getValue[A: Configurable](key: ConfigKey[A]): F[Either[ConfigError, A]]
 
 object Configuration:
 
   /** Start building a new [[AuditedConfiguration]].
     *
+    * @param source
+    *   The first source relevant to the configuration.
     * @return
     *   Fluent builder for the [[AuditedConfiguration]] class.
     */
-  def audited[F[_]: Sync]: AuditedConfiguration.Builder[F] =
-    AuditedConfiguration.builder[F]
+  def audited[F[_]: Sync](source: ConfigSource[F])
+    : AuditedConfiguration.Builder[F] =
+    AuditedConfiguration.forSource[F](source)
 
   /** Create a new [[AuditedConfiguration]] that reads from the environment.
     *
@@ -23,6 +35,6 @@ object Configuration:
     *   The new [[Configuration]].
     */
   def auditedEnvironmentOnly[F[_]: Sync]: F[Configuration[F]] =
-    audited[F].withEnvironmentSource().build()
+    AuditedConfiguration.forEnvironmentSource[F].build()
 
 end Configuration