diff --git a/checker/src/main/java/dev/cel/checker/Env.java b/checker/src/main/java/dev/cel/checker/Env.java
index 8cc354fb2..613bef166 100644
--- a/checker/src/main/java/dev/cel/checker/Env.java
+++ b/checker/src/main/java/dev/cel/checker/Env.java
@@ -540,6 +540,10 @@ boolean enableTimestampEpoch() {
     return celOptions.enableTimestampEpoch();
   }
 
+  boolean enableUnsignedLongs() {
+    return celOptions.enableUnsignedLongs();
+  }
+
   /** Add an identifier {@code decl} to the environment. */
   @CanIgnoreReturnValue
   private Env addIdent(CelIdentDecl celIdentDecl) {
diff --git a/checker/src/main/java/dev/cel/checker/Standard.java b/checker/src/main/java/dev/cel/checker/Standard.java
index 1781fe559..eaac8c300 100644
--- a/checker/src/main/java/dev/cel/checker/Standard.java
+++ b/checker/src/main/java/dev/cel/checker/Standard.java
@@ -99,6 +99,14 @@ public static Env add(Env env) {
     timestampConversionDeclarations(env.enableTimestampEpoch()).forEach(env::add);
     numericComparisonDeclarations(env.enableHeterogeneousNumericComparisons()).forEach(env::add);
 
+    if (env.enableUnsignedLongs()) {
+      env.add(
+          CelFunctionDecl.newFunctionDeclaration(
+              Function.INT.getFunction(),
+              CelOverloadDecl.newGlobalOverload(
+                  "int64_to_int64", "type conversion (identity)", SimpleType.INT, SimpleType.INT)));
+    }
+
     return env;
   }
 
@@ -384,6 +392,8 @@ private static ImmutableList<CelFunctionDecl> coreFunctionDeclarations() {
     celFunctionDeclBuilder.add(
         CelFunctionDecl.newFunctionDeclaration(
             Function.UINT.getFunction(),
+            CelOverloadDecl.newGlobalOverload(
+                "uint64_to_uint64", "type conversion (identity)", SimpleType.UINT, SimpleType.UINT),
             CelOverloadDecl.newGlobalOverload(
                 "int64_to_uint64", "type conversion", SimpleType.UINT, SimpleType.INT),
             CelOverloadDecl.newGlobalOverload(
@@ -395,6 +405,11 @@ private static ImmutableList<CelFunctionDecl> coreFunctionDeclarations() {
     celFunctionDeclBuilder.add(
         CelFunctionDecl.newFunctionDeclaration(
             Function.DOUBLE.getFunction(),
+            CelOverloadDecl.newGlobalOverload(
+                "double_to_double",
+                "type conversion (identity)",
+                SimpleType.DOUBLE,
+                SimpleType.DOUBLE),
             CelOverloadDecl.newGlobalOverload(
                 "int64_to_double", "type conversion", SimpleType.DOUBLE, SimpleType.INT),
             CelOverloadDecl.newGlobalOverload(
@@ -406,6 +421,11 @@ private static ImmutableList<CelFunctionDecl> coreFunctionDeclarations() {
     celFunctionDeclBuilder.add(
         CelFunctionDecl.newFunctionDeclaration(
             Function.STRING.getFunction(),
+            CelOverloadDecl.newGlobalOverload(
+                "string_to_string",
+                "type conversion (identity)",
+                SimpleType.STRING,
+                SimpleType.STRING),
             CelOverloadDecl.newGlobalOverload(
                 "int64_to_string", "type conversion", SimpleType.STRING, SimpleType.INT),
             CelOverloadDecl.newGlobalOverload(
@@ -423,6 +443,8 @@ private static ImmutableList<CelFunctionDecl> coreFunctionDeclarations() {
     celFunctionDeclBuilder.add(
         CelFunctionDecl.newFunctionDeclaration(
             Function.BYTES.getFunction(),
+            CelOverloadDecl.newGlobalOverload(
+                "bytes_to_bytes", "type conversion (identity)", SimpleType.BYTES, SimpleType.BYTES),
             CelOverloadDecl.newGlobalOverload(
                 "string_to_bytes", "type conversion", SimpleType.BYTES, SimpleType.STRING)));
 
@@ -437,12 +459,24 @@ private static ImmutableList<CelFunctionDecl> coreFunctionDeclarations() {
     celFunctionDeclBuilder.add(
         CelFunctionDecl.newFunctionDeclaration(
             Function.DURATION.getFunction(),
+            CelOverloadDecl.newGlobalOverload(
+                "duration_to_duration",
+                "type conversion (identity)",
+                SimpleType.DURATION,
+                SimpleType.DURATION),
             CelOverloadDecl.newGlobalOverload(
                 "string_to_duration",
                 "type conversion, duration should be end with \"s\", which stands for seconds",
                 SimpleType.DURATION,
                 SimpleType.STRING)));
 
+    // Conversions to boolean
+    celFunctionDeclBuilder.add(
+        CelFunctionDecl.newFunctionDeclaration(
+            Function.BOOL.getFunction(),
+            CelOverloadDecl.newGlobalOverload(
+                "bool_to_bool", "type conversion (identity)", SimpleType.BOOL, SimpleType.BOOL)));
+
     // String functions
     celFunctionDeclBuilder.add(
         CelFunctionDecl.newFunctionDeclaration(
@@ -674,7 +708,12 @@ private static ImmutableList<CelFunctionDecl> timestampConversionDeclarations(bo
                     "Type conversion of strings to timestamps according to RFC3339. Example:"
                         + " \"1972-01-01T10:00:20.021-05:00\".",
                     SimpleType.TIMESTAMP,
-                    SimpleType.STRING));
+                    SimpleType.STRING),
+                CelOverloadDecl.newGlobalOverload(
+                    "timestamp_to_timestamp",
+                    "type conversion (identity)",
+                    SimpleType.TIMESTAMP,
+                    SimpleType.TIMESTAMP));
     if (withEpoch) {
       timestampBuilder.addOverloads(
           CelOverloadDecl.newGlobalOverload(
diff --git a/checker/src/test/resources/standardEnvDump.baseline b/checker/src/test/resources/standardEnvDump.baseline
index a49852d84..5f88f7f50 100644
--- a/checker/src/test/resources/standardEnvDump.baseline
+++ b/checker/src/test/resources/standardEnvDump.baseline
@@ -143,9 +143,11 @@ declare _||_ {
 }
 declare bool {
   value type(bool)
+  function bool_to_bool (bool) -> bool
 }
 declare bytes {
   value type(bytes)
+  function bytes_to_bytes (bytes) -> bytes
   function string_to_bytes (string) -> bytes
 }
 declare contains {
@@ -153,11 +155,13 @@ declare contains {
 }
 declare double {
   value type(double)
+  function double_to_double (double) -> double
   function int64_to_double (int) -> double
   function uint64_to_double (uint) -> double
   function string_to_double (string) -> double
 }
 declare duration {
+  function duration_to_duration (google.protobuf.Duration) -> google.protobuf.Duration
   function string_to_duration (string) -> google.protobuf.Duration
 }
 declare dyn {
@@ -217,6 +221,7 @@ declare int {
   function double_to_int64 (double) -> int
   function string_to_int64 (string) -> int
   function timestamp_to_int64 (google.protobuf.Timestamp) -> int
+  function int64_to_int64 (int) -> int
 }
 declare list {
   value type(list(dyn))
@@ -246,6 +251,7 @@ declare startsWith {
 }
 declare string {
   value type(string)
+  function string_to_string (string) -> string
   function int64_to_string (int) -> string
   function uint64_to_string (uint) -> string
   function double_to_string (double) -> string
@@ -255,6 +261,7 @@ declare string {
 }
 declare timestamp {
   function string_to_timestamp (string) -> google.protobuf.Timestamp
+  function timestamp_to_timestamp (google.protobuf.Timestamp) -> google.protobuf.Timestamp
   function int64_to_timestamp (int) -> google.protobuf.Timestamp
 }
 declare type {
@@ -263,6 +270,7 @@ declare type {
 }
 declare uint {
   value type(uint)
+  function uint64_to_uint64 (uint) -> uint
   function int64_to_uint64 (int) -> uint
   function double_to_uint64 (double) -> uint
   function string_to_uint64 (string) -> uint
diff --git a/runtime/src/main/java/dev/cel/runtime/StandardFunctions.java b/runtime/src/main/java/dev/cel/runtime/StandardFunctions.java
index d7d00fdaa..23a77c0c7 100644
--- a/runtime/src/main/java/dev/cel/runtime/StandardFunctions.java
+++ b/runtime/src/main/java/dev/cel/runtime/StandardFunctions.java
@@ -154,6 +154,8 @@ public static void addNonInlined(
   }
 
   private static void addBoolFunctions(Registrar registrar) {
+    // Identity
+    registrar.add("bool_to_bool", Boolean.class, (Boolean x) -> x);
     // The conditional, logical_or, logical_and, and not_strictly_false functions are special-cased.
     registrar.add("logical_not", Boolean.class, (Boolean x) -> !x);
 
@@ -167,6 +169,8 @@ private static void addBoolFunctions(Registrar registrar) {
   }
 
   private static void addBytesFunctions(Registrar registrar) {
+    // Identity
+    registrar.add("bytes_to_bytes", ByteString.class, (ByteString x) -> x);
     // Bytes ordering functions: <, <=, >=, >
     registrar.add(
         "less_bytes",
@@ -205,6 +209,8 @@ private static void addBytesFunctions(Registrar registrar) {
   }
 
   private static void addDoubleFunctions(Registrar registrar, CelOptions celOptions) {
+    // Identity
+    registrar.add("double_to_double", Double.class, (Double x) -> x);
     // Double ordering functions.
     registrar.add("less_double", Double.class, Double.class, (Double x, Double y) -> x < y);
     registrar.add("less_equals_double", Double.class, Double.class, (Double x, Double y) -> x <= y);
@@ -245,6 +251,8 @@ private static void addDoubleFunctions(Registrar registrar, CelOptions celOption
   }
 
   private static void addDurationFunctions(Registrar registrar) {
+    // Identity
+    registrar.add("duration_to_duration", Duration.class, (Duration x) -> x);
     // Duration ordering functions: <, <=, >=, >
     registrar.add(
         "less_duration",
@@ -307,6 +315,12 @@ private static void addDurationFunctions(Registrar registrar) {
   }
 
   private static void addIntFunctions(Registrar registrar, CelOptions celOptions) {
+    // Identity
+    if (celOptions.enableUnsignedLongs()) {
+      // Note that we require UnsignedLong flag here to avoid ambiguous overloads against
+      // "uint64_to_int64", because they both use the same Java Long class.
+      registrar.add("int64_to_int64", Long.class, (Long x) -> x);
+    }
     // Comparison functions.
     registrar.add("less_int64", Long.class, Long.class, (Long x, Long y) -> x < y);
     registrar.add("less_equals_int64", Long.class, Long.class, (Long x, Long y) -> x <= y);
@@ -499,6 +513,8 @@ private static void addMapFunctions(
   }
 
   private static void addStringFunctions(Registrar registrar, CelOptions celOptions) {
+    // Identity
+    registrar.add("string_to_string", String.class, (String x) -> x);
     // String ordering functions: <, <=, >=, >.
     registrar.add(
         "less_string", String.class, String.class, (String x, String y) -> x.compareTo(y) < 0);
@@ -547,6 +563,8 @@ private static void addStringFunctions(Registrar registrar, CelOptions celOption
   // timestamp_to_milliseconds overload
   @SuppressWarnings("JavaLocalDateTimeGetNano")
   private static void addTimestampFunctions(Registrar registrar) {
+    // Identity
+    registrar.add("timestamp_to_timestamp", Timestamp.class, (Timestamp x) -> x);
     // Timestamp relation operators: <, <=, >=, >
     registrar.add(
         "less_timestamp",
@@ -714,6 +732,8 @@ private static void addTimestampFunctions(Registrar registrar) {
   }
 
   private static void addSignedUintFunctions(Registrar registrar, CelOptions celOptions) {
+    // Identity
+    registrar.add("uint64_to_uint64", Long.class, (Long x) -> x);
     // Uint relation operators: <, <=, >=, >
     registrar.add(
         "less_uint64",
@@ -833,6 +853,8 @@ private static void addSignedUintFunctions(Registrar registrar, CelOptions celOp
   }
 
   private static void addUintFunctions(Registrar registrar, CelOptions celOptions) {
+    // Identity
+    registrar.add("uint64_to_uint64", UnsignedLong.class, (UnsignedLong x) -> x);
     registrar.add(
         "less_uint64",
         UnsignedLong.class,
diff --git a/runtime/src/test/resources/boolConversions.baseline b/runtime/src/test/resources/boolConversions.baseline
new file mode 100644
index 000000000..3d7415aba
--- /dev/null
+++ b/runtime/src/test/resources/boolConversions.baseline
@@ -0,0 +1,4 @@
+Source: bool(true)
+=====>
+bindings: {}
+result:   true
\ No newline at end of file
diff --git a/runtime/src/test/resources/bytesConversions.baseline b/runtime/src/test/resources/bytesConversions.baseline
index 4c1458268..6324929ce 100644
--- a/runtime/src/test/resources/bytesConversions.baseline
+++ b/runtime/src/test/resources/bytesConversions.baseline
@@ -2,3 +2,8 @@ Source: bytes('abc\303')
 =====>
 bindings: {}
 result:   abcÃ
+
+Source: bytes(bytes('abc\303'))
+=====>
+bindings: {}
+result:   abcÃ
\ No newline at end of file
diff --git a/runtime/src/test/resources/doubleConversions.baseline b/runtime/src/test/resources/doubleConversions.baseline
index d15dfe090..682e56edc 100644
--- a/runtime/src/test/resources/doubleConversions.baseline
+++ b/runtime/src/test/resources/doubleConversions.baseline
@@ -18,3 +18,8 @@ Source: double('bad')
 bindings: {}
 error:    evaluation error: For input string: "bad"
 error_code:    BAD_FORMAT
+
+Source: double(1.5)
+=====>
+bindings: {}
+result:   1.5
\ No newline at end of file
diff --git a/runtime/src/test/resources/stringConversions.baseline b/runtime/src/test/resources/stringConversions.baseline
index 7e20cff19..59406fc85 100644
--- a/runtime/src/test/resources/stringConversions.baseline
+++ b/runtime/src/test/resources/stringConversions.baseline
@@ -32,3 +32,8 @@ Source: string(duration('1000000s'))
 =====>
 bindings: {}
 result:   1000000s
+
+Source: string('hello')
+=====>
+bindings: {}
+result:   hello
\ No newline at end of file
diff --git a/runtime/src/test/resources/timeConversions.baseline b/runtime/src/test/resources/timeConversions.baseline
index 18b8fdcb0..cb1c4e886 100644
--- a/runtime/src/test/resources/timeConversions.baseline
+++ b/runtime/src/test/resources/timeConversions.baseline
@@ -54,3 +54,20 @@ declare t1 {
 bindings: {}
 error:    evaluation error: invalid duration format
 error_code:    BAD_FORMAT
+
+Source: duration(duration('15.0s'))
+declare t1 {
+  value google.protobuf.Timestamp
+}
+=====>
+bindings: {}
+result:   seconds: 15
+
+
+Source: timestamp(timestamp(123))
+declare t1 {
+  value google.protobuf.Timestamp
+}
+=====>
+bindings: {}
+result:   seconds: 123
\ No newline at end of file
diff --git a/runtime/src/test/resources/uint64Conversions.baseline b/runtime/src/test/resources/uint64Conversions.baseline
index cfdc61974..fac9bfc52 100644
--- a/runtime/src/test/resources/uint64Conversions.baseline
+++ b/runtime/src/test/resources/uint64Conversions.baseline
@@ -35,3 +35,13 @@ Source: uint('f1')
 bindings: {}
 error:    evaluation error: f1
 error_code:    BAD_FORMAT
+
+Source: uint(1u)
+=====>
+bindings: {}
+result:   1
+
+Source: uint(dyn(1u))
+=====>
+bindings: {}
+result:   1
diff --git a/testing/src/main/java/dev/cel/testing/BaseInterpreterTest.java b/testing/src/main/java/dev/cel/testing/BaseInterpreterTest.java
index 795145508..3b9d63f11 100644
--- a/testing/src/main/java/dev/cel/testing/BaseInterpreterTest.java
+++ b/testing/src/main/java/dev/cel/testing/BaseInterpreterTest.java
@@ -1261,6 +1261,12 @@ public void timeConversions() throws Exception {
     // Not supported.
     source = "duration('inf')";
     runTest(Activation.EMPTY);
+
+    source = "duration(duration('15.0s'))"; // Identity
+    runTest(Activation.EMPTY);
+
+    source = "timestamp(timestamp(123))"; // Identity
+    runTest(Activation.EMPTY);
   }
 
   @Test
@@ -1491,6 +1497,12 @@ public void uint64Conversions() throws Exception {
 
     source = "uint('f1')"; // should error
     runTest(Activation.EMPTY);
+
+    source = "uint(1u)"; // identity
+    runTest(Activation.EMPTY);
+
+    source = "uint(dyn(1u))"; // identity, check dynamic dispatch
+    runTest(Activation.EMPTY);
   }
 
   @Test
@@ -1506,6 +1518,9 @@ public void doubleConversions() throws Exception {
 
     source = "double('bad')";
     runTest(Activation.EMPTY);
+
+    source = "double(1.5)"; // Identity
+    runTest(Activation.EMPTY);
   }
 
   @Test
@@ -1536,6 +1551,9 @@ public void stringConversions() throws Exception {
 
     source = "string(duration('1000000s'))";
     runTest(Activation.EMPTY);
+
+    source = "string('hello')"; // Identity
+    runTest(Activation.EMPTY);
   }
 
   @Test
@@ -1546,10 +1564,19 @@ public void bytes() throws Exception {
     runTest(Activation.EMPTY);
   }
 
+  @Test
+  public void boolConversions() throws Exception {
+    source = "bool(true)";
+    runTest(Activation.EMPTY); // Identity
+  }
+
   @Test
   public void bytesConversions() throws Exception {
     source = "bytes('abc\\303')";
     runTest(Activation.EMPTY); // string converts to abcà in bytes form.
+
+    source = "bytes(bytes('abc\\303'))"; // Identity
+    runTest(Activation.EMPTY);
   }
 
   @Test