diff --git a/tools/aconfig/Android.bp b/tools/aconfig/Android.bp
index b3813bf..e708b8a 100644
--- a/tools/aconfig/Android.bp
+++ b/tools/aconfig/Android.bp
@@ -18,6 +18,7 @@
     srcs: ["src/main.rs"],
     rustlibs: [
         "libaconfig_protos",
+        "libanyhow",
         "libprotobuf",
     ],
 }
diff --git a/tools/aconfig/Cargo.toml b/tools/aconfig/Cargo.toml
index 1e86f89..10cd26b 100644
--- a/tools/aconfig/Cargo.toml
+++ b/tools/aconfig/Cargo.toml
@@ -9,6 +9,7 @@
 cargo = []
 
 [dependencies]
+anyhow = "1.0.69"
 protobuf = "3.2.0"
 
 [build-dependencies]
diff --git a/tools/aconfig/protos/aconfig.proto b/tools/aconfig/protos/aconfig.proto
index 989c398..7d0e8ad 100644
--- a/tools/aconfig/protos/aconfig.proto
+++ b/tools/aconfig/protos/aconfig.proto
@@ -12,12 +12,29 @@
 // See the License for the specific language governing permissions and
 // limitations under the License
 
-// Placeholder proto file. Will be replaced by actual contents.
+// This is the schema definition for of Aconfig files. Modifications need to be
+// either backwards compatible, or include updates to all Aconfig files in the
+// Android tree.
 
-syntax = "proto3";
+syntax = "proto2";
 
 package android.aconfig;
 
-message Placeholder {
-  string name = 1;
-}
+message flag {
+  required string id = 1;
+  required string description = 2;
+  required bool value = 3;
+};
+
+message android_config {
+  repeated flag flag = 1;
+};
+
+message override {
+  required string id = 1;
+  required bool value = 2;
+};
+
+message override_config {
+  repeated override override = 1;
+};
diff --git a/tools/aconfig/src/aconfig.rs b/tools/aconfig/src/aconfig.rs
new file mode 100644
index 0000000..a6e1d1b
--- /dev/null
+++ b/tools/aconfig/src/aconfig.rs
@@ -0,0 +1,159 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+use anyhow::{anyhow, Context, Error, Result};
+
+use crate::protos::{ProtoAndroidConfig, ProtoFlag, ProtoOverride, ProtoOverrideConfig};
+
+#[derive(Debug, PartialEq, Eq)]
+pub struct Flag {
+    pub id: String,
+    pub description: String,
+    pub value: bool,
+}
+
+impl Flag {
+    pub fn try_from_text_proto(text_proto: &str) -> Result<Flag> {
+        let proto: ProtoFlag = crate::protos::try_from_text_proto(text_proto)
+            .with_context(|| text_proto.to_owned())?;
+        proto.try_into()
+    }
+
+    pub fn try_from_text_proto_list(text_proto: &str) -> Result<Vec<Flag>> {
+        let proto: ProtoAndroidConfig = crate::protos::try_from_text_proto(text_proto)
+            .with_context(|| text_proto.to_owned())?;
+        proto.flag.into_iter().map(|proto_flag| proto_flag.try_into()).collect()
+    }
+}
+
+impl TryFrom<ProtoFlag> for Flag {
+    type Error = Error;
+
+    fn try_from(proto: ProtoFlag) -> Result<Self, Self::Error> {
+        let Some(id) = proto.id else {
+            return Err(anyhow!("missing 'id' field"));
+        };
+        let Some(description) = proto.description else {
+            return Err(anyhow!("missing 'description' field"));
+        };
+        let Some(value) = proto.value else {
+            return Err(anyhow!("missing 'value' field"));
+        };
+        Ok(Flag { id, description, value })
+    }
+}
+
+#[derive(Debug, PartialEq, Eq)]
+pub struct Override {
+    pub id: String,
+    pub value: bool,
+}
+
+impl Override {
+    pub fn try_from_text_proto(text_proto: &str) -> Result<Override> {
+        let proto: ProtoOverride = crate::protos::try_from_text_proto(text_proto)?;
+        proto.try_into()
+    }
+
+    pub fn try_from_text_proto_list(text_proto: &str) -> Result<Vec<Override>> {
+        let proto: ProtoOverrideConfig = crate::protos::try_from_text_proto(text_proto)?;
+        proto.override_.into_iter().map(|proto_flag| proto_flag.try_into()).collect()
+    }
+}
+
+impl TryFrom<ProtoOverride> for Override {
+    type Error = Error;
+
+    fn try_from(proto: ProtoOverride) -> Result<Self, Self::Error> {
+        let Some(id) = proto.id else {
+            return Err(anyhow!("missing 'id' field"));
+        };
+        let Some(value) = proto.value else {
+            return Err(anyhow!("missing 'value' field"));
+        };
+        Ok(Override { id, value })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_flag_try_from_text_proto() {
+        let expected = Flag {
+            id: "1234".to_owned(),
+            description: "Description of the flag".to_owned(),
+            value: true,
+        };
+
+        let s = r#"
+        id: "1234"
+        description: "Description of the flag"
+        value: true
+        "#;
+        let actual = Flag::try_from_text_proto(s).unwrap();
+
+        assert_eq!(expected, actual);
+    }
+
+    #[test]
+    fn test_flag_try_from_text_proto_missing_field() {
+        let s = r#"
+        description: "Description of the flag"
+        value: true
+        "#;
+        let error = Flag::try_from_text_proto(s).unwrap_err();
+        assert!(format!("{:?}", error).contains("Message not initialized"));
+    }
+
+    #[test]
+    fn test_flag_try_from_text_proto_list() {
+        let expected = vec![
+            Flag { id: "a".to_owned(), description: "A".to_owned(), value: true },
+            Flag { id: "b".to_owned(), description: "B".to_owned(), value: false },
+        ];
+
+        let s = r#"
+        flag {
+            id: "a"
+            description: "A"
+            value: true
+        }
+        flag {
+            id: "b"
+            description: "B"
+            value: false
+        }
+        "#;
+        let actual = Flag::try_from_text_proto_list(s).unwrap();
+
+        assert_eq!(expected, actual);
+    }
+
+    #[test]
+    fn test_override_try_from_text_proto_list() {
+        let expected = Override { id: "1234".to_owned(), value: true };
+
+        let s = r#"
+        id: "1234"
+        value: true
+        "#;
+        let actual = Override::try_from_text_proto(s).unwrap();
+
+        assert_eq!(expected, actual);
+    }
+}
diff --git a/tools/aconfig/src/main.rs b/tools/aconfig/src/main.rs
index 5414f0e..9d87ca4 100644
--- a/tools/aconfig/src/main.rs
+++ b/tools/aconfig/src/main.rs
@@ -16,40 +16,23 @@
 
 //! `aconfig` is a build time tool to manage build time configurations, such as feature flags.
 
-use protobuf::text_format::{parse_from_str, ParseError};
+use anyhow::Result;
 
+mod aconfig;
 mod protos;
-use protos::Placeholder;
 
-fn foo() -> Result<String, ParseError> {
-    let placeholder = parse_from_str::<Placeholder>(r#"name: "aconfig""#)?;
-    Ok(placeholder.name)
-}
+use aconfig::{Flag, Override};
 
-fn main() {
-    println!("{:?}", foo());
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn test_foo() {
-        assert_eq!("aconfig", foo().unwrap());
-    }
-
-    #[test]
-    fn test_binary_protobuf() {
-        use protobuf::Message;
-        let mut buffer = Vec::new();
-
-        let mut original = Placeholder::new();
-        original.name = "test".to_owned();
-        original.write_to_writer(&mut buffer).unwrap();
-
-        let copy = Placeholder::parse_from_reader(&mut buffer.as_slice()).unwrap();
-
-        assert_eq!(original, copy);
-    }
+fn main() -> Result<()> {
+    let flag = Flag::try_from_text_proto(r#"id: "a" description: "description of a" value: true"#)?;
+    println!("{:?}", flag);
+    let flags = Flag::try_from_text_proto_list(
+        r#"flag { id: "a" description: "description of a" value: true }"#,
+    )?;
+    println!("{:?}", flags);
+    let override_ = Override::try_from_text_proto(r#"id: "foo" value: true"#)?;
+    println!("{:?}", override_);
+    let overrides = Override::try_from_text_proto_list(r#"override { id: "foo" value: true }"#)?;
+    println!("{:?}", overrides);
+    Ok(())
 }
diff --git a/tools/aconfig/src/protos.rs b/tools/aconfig/src/protos.rs
index 99d584a..42a7c1a 100644
--- a/tools/aconfig/src/protos.rs
+++ b/tools/aconfig/src/protos.rs
@@ -26,13 +26,42 @@
 //
 // This module hides these differences from the rest of aconfig.
 
-// When building with the Android tool-chain:
+// ---- When building with the Android tool-chain ----
 #[cfg(not(feature = "cargo"))]
-pub use aconfig_protos::aconfig::Placeholder;
+pub use aconfig_protos::aconfig::Android_config as ProtoAndroidConfig;
 
-// When building with cargo:
+#[cfg(not(feature = "cargo"))]
+pub use aconfig_protos::aconfig::Flag as ProtoFlag;
+
+#[cfg(not(feature = "cargo"))]
+pub use aconfig_protos::aconfig::Override_config as ProtoOverrideConfig;
+
+#[cfg(not(feature = "cargo"))]
+pub use aconfig_protos::aconfig::Override as ProtoOverride;
+
+// ---- When building with cargo ----
 #[cfg(feature = "cargo")]
 include!(concat!(env!("OUT_DIR"), "/aconfig_proto/mod.rs"));
 
 #[cfg(feature = "cargo")]
-pub use aconfig::Placeholder;
+pub use aconfig::Android_config as ProtoAndroidConfig;
+
+#[cfg(feature = "cargo")]
+pub use aconfig::Flag as ProtoFlag;
+
+#[cfg(feature = "cargo")]
+pub use aconfig::Override_config as ProtoOverrideConfig;
+
+#[cfg(feature = "cargo")]
+pub use aconfig::Override as ProtoOverride;
+
+// ---- Common for both the Android tool-chain and cargo ----
+use anyhow::Result;
+
+pub fn try_from_text_proto<T>(s: &str) -> Result<T>
+where
+    T: protobuf::MessageFull,
+{
+    // warning: parse_from_str does not check if required fields are set
+    protobuf::text_format::parse_from_str(s).map_err(|e| e.into())
+}