diff --git a/packages/rules/src/auditability/docs/missing_natspec.rs b/packages/rules/src/auditability/docs/missing_natspec.rs
new file mode 100644
index 0000000..384670b
--- /dev/null
+++ b/packages/rules/src/auditability/docs/missing_natspec.rs
@@ -0,0 +1,72 @@
+//! Detect Missing NatSpec Documentation
+//!
+//! Flags public/external functions that lack NatSpec (`///` or `/** */`) comments.
+//! Poor documentation reduces auditability and maintainability.
+
+use crate::rule_engine::{Rule, RuleViolation, ViolationSeverity};
+use syn::{Item, Visibility};
+
+pub struct MissingNatspecRule;
+
+impl Rule for MissingNatspecRule {
+    fn name(&self) -> &str {
+        "missing-natspec"
+    }
+
+    fn description(&self) -> &str {
+        "Detects public functions missing NatSpec documentation comments."
+    }
+
+    fn check(&self, ast: &[Item]) -> Vec<RuleViolation> {
+        let mut violations = Vec::new();
+        for item in ast {
+            if let Item::Fn(func) = item {
+                let is_public = matches!(func.vis, Visibility::Public(_));
+                let has_doc = func.attrs.iter().any(|a| a.path().is_ident("doc"));
+                if is_public && !has_doc {
+                    violations.push(RuleViolation {
+                        rule_name: self.name().to_string(),
+                        description: format!(
+                            "Public function `{}` is missing NatSpec documentation.",
+                            func.sig.ident
+                        ),
+                        severity: ViolationSeverity::Low,
+                        line_number: 0,
+                        column_number: 0,
+                        variable_name: func.sig.ident.to_string(),
+                        suggestion: "Add `/// @notice`, `/// @param`, and `/// @return` \
+                            NatSpec comments above the function."
+                            .to_string(),
+                    });
+                }
+            }
+        }
+        violations
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use syn::parse_file;
+
+    fn check(code: &str) -> Vec<RuleViolation> {
+        let ast = parse_file(code).expect("parse failed");
+        MissingNatspecRule.check(&ast.items)
+    }
+
+    #[test]
+    fn flags_undocumented_public_fn() {
+        assert!(!check("pub fn transfer() {}").is_empty());
+    }
+
+    #[test]
+    fn no_violation_for_documented_fn() {
+        assert!(check("/// @notice transfers tokens\npub fn transfer() {}").is_empty());
+    }
+
+    #[test]
+    fn no_violation_for_private_fn() {
+        assert!(check("fn internal_helper() {}").is_empty());
+    }
+}
\ No newline at end of file
diff --git a/packages/rules/src/auditability/docs/mod.rs b/packages/rules/src/auditability/docs/mod.rs
new file mode 100644
index 0000000..a4010a1
--- /dev/null
+++ b/packages/rules/src/auditability/docs/mod.rs
@@ -0,0 +1,2 @@
+pub mod missing_natspec;
+pub use missing_natspec::MissingNatspecRule;
\ No newline at end of file
diff --git a/packages/rules/src/auditability/mod.rs b/packages/rules/src/auditability/mod.rs
new file mode 100644
index 0000000..e68002c
--- /dev/null
+++ b/packages/rules/src/auditability/mod.rs
@@ -0,0 +1,2 @@
+pub mod docs;
+pub use docs::MissingNatspecRule;
\ No newline at end of file
diff --git a/packages/rules/src/security/external_calls/external_calls_in_loops.rs b/packages/rules/src/security/external_calls/external_calls_in_loops.rs
new file mode 100644
index 0000000..fe143a3
--- /dev/null
+++ b/packages/rules/src/security/external_calls/external_calls_in_loops.rs
@@ -0,0 +1,78 @@
+//! Detect External Calls Inside Loops
+//!
+//! Flags external function calls that appear inside loop bodies.
+//! This pattern increases gas costs and expands the reentrancy attack surface.
+
+use crate::rule_engine::{Rule, RuleViolation, ViolationSeverity};
+use syn::{Expr, Item, Stmt};
+
+pub struct ExternalCallsInLoopsRule;
+
+impl Rule for ExternalCallsInLoopsRule {
+    fn name(&self) -> &str {
+        "external-calls-in-loops"
+    }
+
+    fn description(&self) -> &str {
+        "Detects external calls inside loop bodies. \
+         This increases gas risk and expands the reentrancy attack surface."
+    }
+
+    fn check(&self, ast: &[Item]) -> Vec<RuleViolation> {
+        let mut violations = Vec::new();
+        for item in ast {
+            if let Item::Fn(func) = item {
+                self.check_stmts(&func.block.stmts, &mut violations);
+            }
+        }
+        violations
+    }
+}
+
+impl ExternalCallsInLoopsRule {
+    fn check_stmts(&self, stmts: &[Stmt], violations: &mut Vec<RuleViolation>) {
+        for stmt in stmts {
+            if let Stmt::Expr(Expr::ForLoop(loop_expr), _) = stmt {
+                self.check_loop_body(&loop_expr.body.stmts, violations);
+            }
+            if let Stmt::Expr(Expr::While(loop_expr), _) = stmt {
+                self.check_loop_body(&loop_expr.body.stmts, violations);
+            }
+        }
+    }
+
+    fn check_loop_body(&self, stmts: &[Stmt], violations: &mut Vec<RuleViolation>) {
+        for stmt in stmts {
+            if let Stmt::Expr(Expr::MethodCall(call), _) = stmt {
+                let method = call.method.to_string();
+                if matches!(method.as_str(), "transfer" | "call" | "send" | "invoke") {
+                    violations.push(RuleViolation {
+                        rule_name: self.name().to_string(),
+                        description: format!(
+                            "External call `{}` inside a loop increases gas and reentrancy risk.",
+                            method
+                        ),
+                        severity: ViolationSeverity::High,
+                        line_number: 0,
+                        column_number: 0,
+                        variable_name: method,
+                        suggestion: "Collect results in the loop and perform external calls after."
+                            .to_string(),
+                    });
+                }
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use syn::parse_file;
+
+    #[test]
+    fn no_violation_no_loop() {
+        let ast = parse_file("fn f() { x.transfer(1); }").expect("parse");
+        assert!(ExternalCallsInLoopsRule.check(&ast.items).is_empty());
+    }
+}
\ No newline at end of file
diff --git a/packages/rules/src/security/external_calls/mod.rs b/packages/rules/src/security/external_calls/mod.rs
new file mode 100644
index 0000000..d7585f0
--- /dev/null
+++ b/packages/rules/src/security/external_calls/mod.rs
@@ -0,0 +1,2 @@
+pub mod external_calls_in_loops;
+pub use external_calls_in_loops::ExternalCallsInLoopsRule;
\ No newline at end of file