diff --git a/easy-rules-core/src/main/java/org/jeasy/rules/api/Facts.java b/easy-rules-core/src/main/java/org/jeasy/rules/api/Facts.java
index 723504d..5b28a6f 100644
--- a/easy-rules-core/src/main/java/org/jeasy/rules/api/Facts.java
+++ b/easy-rules-core/src/main/java/org/jeasy/rules/api/Facts.java
@@ -27,18 +27,40 @@ import java.util.*;
 
 import static java.lang.String.format;
 
+/**
+ * Represents a set of named facts. Facts have unique name within a <code>Facts</code> object.
+ *
+ * @author Mahmoud Ben Hassine (mahmoud.benhassine@icloud.com)
+ */
 public class Facts implements Iterable<Map.Entry<String, Object>> {
 
     private Map<String, Object> facts = new HashMap<>();
 
+    /**
+     * Add a fact.
+     *
+     * @param name fact name
+     * @param fact object
+     */
     public void add(String name, Object fact) {
         facts.put(name, fact);
     }
 
+    /**
+     * Remove fact.
+     *
+     * @param name of fact to remove
+     */
     public void remove(String name) {
         facts.remove(name);
     }
 
+    /**
+     * Get a fact by name.
+     *
+     * @param name of fact to get.
+     * @return the fact having the given name, or null if there is no fact with the given name
+     */
     public Object get(String name) {
         return facts.get(name);
     }
diff --git a/easy-rules-core/src/main/java/org/jeasy/rules/api/Rules.java b/easy-rules-core/src/main/java/org/jeasy/rules/api/Rules.java
index ed4ebdb..bca7307 100644
--- a/easy-rules-core/src/main/java/org/jeasy/rules/api/Rules.java
+++ b/easy-rules-core/src/main/java/org/jeasy/rules/api/Rules.java
@@ -30,36 +30,75 @@ import java.util.Iterator;
 import java.util.Set;
 import java.util.TreeSet;
 
+/**
+ * This class encapsulates a set of rules and represents a rules namespace.
+ * Rules must have a unique name within a rules namespace.
+ *
+ * @author Mahmoud Ben Hassine (mahmoud.benhassine@icloud.com)
+ */
 public class Rules implements Iterable<Rule> {
 
     private Set<Rule> rules = new TreeSet<>();
 
+    /**
+     * Create a new {@link Rules} object.
+     *
+     * @param rules to register
+     */
     public Rules(Set<Rule> rules) {
         this.rules = rules;
     }
 
+    /**
+     * Create a new {@link Rules} object.
+     *
+     * @param rules to register
+     */
     public Rules(Rule... rules ) {
         Collections.addAll(this.rules, rules);
     }
 
+    /**
+     * Create a new {@link Rules} object.
+     *
+     * @param rules to register
+     */
     public Rules(Object... rules ) {
         for (Object rule : rules) {
             this.register(RuleProxy.asRule(rule));
         }
     }
 
+    /**
+     * Register a new rule.
+     *
+     * @param rule to register
+     */
     public void register(Object rule) {
         rules.add(RuleProxy.asRule(rule));
     }
 
+    /**
+     * Unregister a rule.
+     *
+     * @param rule to unregister
+     */
     public void unregister(Object rule) {
         rules.remove(RuleProxy.asRule(rule));
     }
 
+    /**
+     * Check if the rule set is empty.
+     *
+     * @return true if the rule set is empty, false otherwise
+     */
     public boolean isEmpty() {
         return rules.isEmpty();
     }
 
+    /**
+     * Clear rules.
+     */
     public void clear() {
         rules.clear();
     }
@@ -69,6 +108,9 @@ public class Rules implements Iterable<Rule> {
         return rules.iterator();
     }
 
+    /**
+     * Sort rules.
+     */
     public void sort() {
         rules = new TreeSet<>(rules);
     }
diff --git a/easy-rules-core/src/main/java/org/jeasy/rules/core/RuleProxy.java b/easy-rules-core/src/main/java/org/jeasy/rules/core/RuleProxy.java
index a743095..d2522b9 100644
--- a/easy-rules-core/src/main/java/org/jeasy/rules/core/RuleProxy.java
+++ b/easy-rules-core/src/main/java/org/jeasy/rules/core/RuleProxy.java
@@ -36,6 +36,11 @@ import java.lang.reflect.Method;
 import java.lang.reflect.Proxy;
 import java.util.*;
 
+/**
+ * Main class to create rule proxies from annotated objects.
+ *
+ * @author Mahmoud Ben Hassine (mahmoud.benhassine@icloud.com)
+ */
 public class RuleProxy implements InvocationHandler {
 
     private Object target;
diff --git a/easy-rules-core/src/main/java/org/jeasy/rules/core/RulesEngineBuilder.java b/easy-rules-core/src/main/java/org/jeasy/rules/core/RulesEngineBuilder.java
index a698712..413ffd8 100644
--- a/easy-rules-core/src/main/java/org/jeasy/rules/core/RulesEngineBuilder.java
+++ b/easy-rules-core/src/main/java/org/jeasy/rules/core/RulesEngineBuilder.java
@@ -40,6 +40,11 @@ public class RulesEngineBuilder {
 
     private List<RuleListener> ruleListeners;
 
+    /**
+     * Create a new rules engine builder.
+     *
+     * @return a new rules engine builder
+     */
     public static RulesEngineBuilder aNewRulesEngine() {
         return new RulesEngineBuilder();
     }
@@ -55,36 +60,77 @@ public class RulesEngineBuilder {
         return this;
     }
 
+    /**
+     * Set the <code>setSkipOnFirstAppliedRule</code> parameter.
+     *
+     * @param skipOnFirstAppliedRule to set
+     * @return the rules engine builder
+     */
     public RulesEngineBuilder withSkipOnFirstAppliedRule(final boolean skipOnFirstAppliedRule) {
         parameters.setSkipOnFirstAppliedRule(skipOnFirstAppliedRule);
         return this;
     }
 
+    /**
+     * Set the <code>skipOnFirstNonTriggeredRule</code> parameter.
+     *
+     * @param skipOnFirstNonTriggeredRule to set
+     * @return the rules engine builder
+     */
     public RulesEngineBuilder withSkipOnFirstNonTriggeredRule(final boolean skipOnFirstNonTriggeredRule) {
         parameters.setSkipOnFirstNonTriggeredRule(skipOnFirstNonTriggeredRule);
         return this;
     }
 
+    /**
+     * Set <code>skipOnFirstFailedRule</code> parameter.
+     *
+     * @param skipOnFirstFailedRule to set
+     * @return the rules engine builder
+     */
     public RulesEngineBuilder withSkipOnFirstFailedRule(final boolean skipOnFirstFailedRule) {
         parameters.setSkipOnFirstFailedRule(skipOnFirstFailedRule);
         return this;
     }
 
+    /**
+     * Set rule priority threshold.
+     *
+     * @param priorityThreshold to set
+     * @return the rules engine builder
+     */
     public RulesEngineBuilder withRulePriorityThreshold(final int priorityThreshold) {
         parameters.setPriorityThreshold(priorityThreshold);
         return this;
     }
 
+    /**
+     * Register a rule listener.
+     *
+     * @param ruleListener to register
+     * @return the rules engine builder
+     */
     public RulesEngineBuilder withRuleListener(final RuleListener ruleListener) {
         this.ruleListeners.add(ruleListener);
         return this;
     }
 
+    /**
+     * Set silent mode to mute all loggers.
+     *
+     * @param silentMode to set
+     * @return the rules engine builder
+     */
     public RulesEngineBuilder withSilentMode(final boolean silentMode) {
         parameters.setSilentMode(silentMode);
         return this;
     }
 
+    /**
+     * Build a rules engine instance.
+     *
+     * @return a rules engine instance
+     */
     public RulesEngine build() {
         return new DefaultRulesEngine(parameters, ruleListeners);
     }
diff --git a/easy-rules-core/src/main/java/org/jeasy/rules/core/Utils.java b/easy-rules-core/src/main/java/org/jeasy/rules/core/Utils.java
index dbe88b3..2aa6251 100644
--- a/easy-rules-core/src/main/java/org/jeasy/rules/core/Utils.java
+++ b/easy-rules-core/src/main/java/org/jeasy/rules/core/Utils.java
@@ -35,11 +35,6 @@ import java.util.logging.Logger;
 
 import static java.util.Arrays.asList;
 
-/**
- * Utilities class.
- *
- * @author Mahmoud Ben Hassine (mahmoud.benhassine@icloud.com)
- */
 final class Utils {
 
     private static final Logger LOGGER = Logger.getLogger(Utils.class.getName());