diff --git a/compos/aidl/com/android/compos/InputFdAnnotation.aidl b/compos/aidl/com/android/compos/FdAnnotation.aidl
similarity index 61%
rename from compos/aidl/com/android/compos/InputFdAnnotation.aidl
rename to compos/aidl/com/android/compos/FdAnnotation.aidl
index 44a5591..b910391 100644
--- a/compos/aidl/com/android/compos/InputFdAnnotation.aidl
+++ b/compos/aidl/com/android/compos/FdAnnotation.aidl
@@ -17,13 +17,16 @@
 package com.android.compos;
 
 /** {@hide} */
-parcelable InputFdAnnotation {
+parcelable FdAnnotation {
     /**
-     * File descriptor number to be passed to the program.  This is also the same file descriptor
-     * number used in the backend server.
+     * Input file descriptor numbers to be passed to the program.  This is currently assumed to be
+     * same as the file descriptor number used in the backend server.
      */
-    int fd;
+    int[] input_fds;
 
-    /** The actual file size in bytes of the backing file to be read. */
-    long file_size;
+    /**
+     * Output file descriptor numbers to be passed to the program.  This is currently assumed to be
+     * same as the file descriptor number used in the backend server.
+     */
+    int[] output_fds;
 }
diff --git a/compos/aidl/com/android/compos/ICompOsService.aidl b/compos/aidl/com/android/compos/ICompOsService.aidl
index 3a74940..7904130 100644
--- a/compos/aidl/com/android/compos/ICompOsService.aidl
+++ b/compos/aidl/com/android/compos/ICompOsService.aidl
@@ -18,7 +18,7 @@
 
 import com.android.compos.CompOsKeyData;
 import com.android.compos.CompilationResult;
-import com.android.compos.Metadata;
+import com.android.compos.FdAnnotation;
 
 /** {@hide} */
 interface ICompOsService {
@@ -33,17 +33,17 @@
     void initializeSigningKey(in byte[] keyBlob);
 
     /**
-     * Run dex2oat command with provided args, in a context that may be specified in the Metadata,
+     * Run dex2oat command with provided args, in a context that may be specified in FdAnnotation,
      * e.g. with file descriptors pre-opened. The service is responsible to decide what executables
      * it may run.
      *
      * @param args The command line arguments to run. The 0-th args is normally the program name,
      *             which may not be used by the service. The service may be configured to always use
      *             a fixed executable, or possibly use the 0-th args are the executable lookup hint.
-     * @param metadata Additional information of the execution
+     * @param fd_annotation Additional file descriptor information of the execution
      * @return a CompilationResult
      */
-    CompilationResult compile(in String[] args, in Metadata metadata);
+    CompilationResult compile(in String[] args, in FdAnnotation fd_annotation);
 
     /**
      * Generate a new public/private key pair suitable for signing CompOs output files.
diff --git a/compos/aidl/com/android/compos/Metadata.aidl b/compos/aidl/com/android/compos/Metadata.aidl
deleted file mode 100644
index a15214d..0000000
--- a/compos/aidl/com/android/compos/Metadata.aidl
+++ /dev/null
@@ -1,26 +0,0 @@
-/*
- * Copyright (C) 2021 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.
- */
-
-package com.android.compos;
-
-import com.android.compos.InputFdAnnotation;
-import com.android.compos.OutputFdAnnotation;
-
-/** {@hide} */
-parcelable Metadata {
-    InputFdAnnotation[] input_fd_annotations;
-    OutputFdAnnotation[] output_fd_annotations;
-}
diff --git a/compos/aidl/com/android/compos/OutputFdAnnotation.aidl b/compos/aidl/com/android/compos/OutputFdAnnotation.aidl
deleted file mode 100644
index 95ce425..0000000
--- a/compos/aidl/com/android/compos/OutputFdAnnotation.aidl
+++ /dev/null
@@ -1,26 +0,0 @@
-/*
- * Copyright (C) 2021 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.
- */
-
-package com.android.compos;
-
-/** {@hide} */
-parcelable OutputFdAnnotation {
-    /**
-     * File descriptor number to be passed to the program.  This is currently assumed to be same as
-     * the file descriptor number used in the backend server.
-     */
-    int fd;
-}
diff --git a/compos/src/compilation.rs b/compos/src/compilation.rs
index 0199eb5..fec82a6 100644
--- a/compos/src/compilation.rs
+++ b/compos/src/compilation.rs
@@ -27,7 +27,7 @@
     InputFdAnnotation::InputFdAnnotation, OutputFdAnnotation::OutputFdAnnotation,
 };
 use authfs_aidl_interface::binder::{ParcelFileDescriptor, Strong};
-use compos_aidl_interface::aidl::com::android::compos::Metadata::Metadata;
+use compos_aidl_interface::aidl::com::android::compos::FdAnnotation::FdAnnotation;
 
 /// The number that represents the file descriptor number expecting by the task. The number may be
 /// meaningless in the current process.
@@ -50,17 +50,17 @@
     image: ParcelFileDescriptor,
 }
 
-/// Runs the compiler with given flags with file descriptors described in `metadata` retrieved via
-/// `authfs_service`. Returns exit code of the compiler process.
+/// Runs the compiler with given flags with file descriptors described in `fd_annotation` retrieved
+/// via `authfs_service`. Returns exit code of the compiler process.
 pub fn compile(
     compiler_path: &Path,
     compiler_args: &[String],
     authfs_service: Strong<dyn IAuthFsService>,
-    metadata: &Metadata,
+    fd_annotation: &FdAnnotation,
 ) -> Result<CompilerOutput> {
     // Mount authfs (via authfs_service). The authfs instance unmounts once the `authfs` variable
     // is out of scope.
-    let authfs_config = build_authfs_config(metadata);
+    let authfs_config = build_authfs_config(fd_annotation);
     let authfs = authfs_service.mount(&authfs_config)?;
 
     // The task expects to receive FD numbers that match its flags (e.g. --zip-fd=42) prepared
@@ -135,18 +135,18 @@
     })
 }
 
-fn build_authfs_config(metadata: &Metadata) -> AuthFsConfig {
+fn build_authfs_config(fd_annotation: &FdAnnotation) -> AuthFsConfig {
     AuthFsConfig {
         port: 3264, // TODO: support dynamic port
-        inputFdAnnotations: metadata
-            .input_fd_annotations
+        inputFdAnnotations: fd_annotation
+            .input_fds
             .iter()
-            .map(|x| InputFdAnnotation { fd: x.fd, fileSize: x.file_size })
+            .map(|fd| InputFdAnnotation { fd: *fd })
             .collect(),
-        outputFdAnnotations: metadata
-            .output_fd_annotations
+        outputFdAnnotations: fd_annotation
+            .output_fds
             .iter()
-            .map(|x| OutputFdAnnotation { fd: x.fd })
+            .map(|fd| OutputFdAnnotation { fd: *fd })
             .collect(),
     }
 }
diff --git a/compos/src/compsvc.rs b/compos/src/compsvc.rs
index 4a19030..ed5534e 100644
--- a/compos/src/compsvc.rs
+++ b/compos/src/compsvc.rs
@@ -32,8 +32,8 @@
 use compos_aidl_interface::aidl::com::android::compos::{
     CompOsKeyData::CompOsKeyData,
     CompilationResult::CompilationResult,
+    FdAnnotation::FdAnnotation,
     ICompOsService::{BnCompOsService, ICompOsService},
-    Metadata::Metadata,
 };
 use compos_aidl_interface::binder::{
     BinderFeatures, ExceptionCode, Interface, Result as BinderResult, Status, Strong,
@@ -85,14 +85,19 @@
         }
     }
 
-    fn compile(&self, args: &[String], metadata: &Metadata) -> BinderResult<CompilationResult> {
+    fn compile(
+        &self,
+        args: &[String],
+        fd_annotation: &FdAnnotation,
+    ) -> BinderResult<CompilationResult> {
         let authfs_service = get_authfs_service()?;
-        let output = compile(&self.dex2oat_path, args, authfs_service, metadata).map_err(|e| {
-            new_binder_exception(
-                ExceptionCode::SERVICE_SPECIFIC,
-                format!("Compilation failed: {}", e),
-            )
-        })?;
+        let output =
+            compile(&self.dex2oat_path, args, authfs_service, fd_annotation).map_err(|e| {
+                new_binder_exception(
+                    ExceptionCode::SERVICE_SPECIFIC,
+                    format!("Compilation failed: {}", e),
+                )
+            })?;
         match output {
             CompilerOutput::Digests { oat, vdex, image } => {
                 let key = &*self.key_blob.read().unwrap();
diff --git a/compos/src/pvm_exec.rs b/compos/src/pvm_exec.rs
index 99eddfc..27802e3 100644
--- a/compos/src/pvm_exec.rs
+++ b/compos/src/pvm_exec.rs
@@ -32,14 +32,12 @@
 use log::{debug, error, warn};
 use minijail::Minijail;
 use nix::fcntl::{fcntl, FcntlArg::F_GETFD};
-use nix::sys::stat::fstat;
 use std::os::unix::io::RawFd;
 use std::path::Path;
 use std::process::exit;
 
 use compos_aidl_interface::aidl::com::android::compos::{
-    ICompOsService::ICompOsService, InputFdAnnotation::InputFdAnnotation, Metadata::Metadata,
-    OutputFdAnnotation::OutputFdAnnotation,
+    FdAnnotation::FdAnnotation, ICompOsService::ICompOsService,
 };
 use compos_aidl_interface::binder::Strong;
 
@@ -65,7 +63,7 @@
     }
 }
 
-fn spawn_fd_server(metadata: &Metadata, debuggable: bool) -> Result<Minijail> {
+fn spawn_fd_server(fd_annotation: &FdAnnotation, debuggable: bool) -> Result<Minijail> {
     let mut inheritable_fds = if debuggable {
         vec![1, 2] // inherit/redirect stdout/stderr for debugging
     } else {
@@ -73,15 +71,15 @@
     };
 
     let mut args = vec![FD_SERVER_BIN.to_string(), "--rpc-binder".to_string()];
-    for metadata in &metadata.input_fd_annotations {
+    for fd in &fd_annotation.input_fds {
         args.push("--ro-fds".to_string());
-        args.push(metadata.fd.to_string());
-        inheritable_fds.push(metadata.fd);
+        args.push(fd.to_string());
+        inheritable_fds.push(*fd);
     }
-    for metadata in &metadata.output_fd_annotations {
+    for fd in &fd_annotation.output_fds {
         args.push("--rw-fds".to_string());
-        args.push(metadata.fd.to_string());
-        inheritable_fds.push(metadata.fd);
+        args.push(fd.to_string());
+        inheritable_fds.push(*fd);
     }
 
     let jail = Minijail::new()?;
@@ -104,7 +102,7 @@
 
 struct Config {
     args: Vec<String>,
-    metadata: Metadata,
+    fd_annotation: FdAnnotation,
     cid: Option<u32>,
     debuggable: bool,
 }
@@ -133,38 +131,20 @@
              .multiple(true))
         .get_matches();
 
-    let results: Result<Vec<_>> = matches
-        .values_of("in-fd")
-        .unwrap_or_default()
-        .map(|arg| {
-            let fd = parse_arg_fd(arg)?;
-            let file_size = fstat(fd)?.st_size;
-            Ok(InputFdAnnotation { fd, file_size })
-        })
-        .collect();
-    let input_fd_annotations = results?;
+    let results: Result<Vec<_>> =
+        matches.values_of("in-fd").unwrap_or_default().map(parse_arg_fd).collect();
+    let input_fds = results?;
 
-    let results: Result<Vec<_>> = matches
-        .values_of("out-fd")
-        .unwrap_or_default()
-        .map(|arg| {
-            let fd = parse_arg_fd(arg)?;
-            Ok(OutputFdAnnotation { fd })
-        })
-        .collect();
-    let output_fd_annotations = results?;
+    let results: Result<Vec<_>> =
+        matches.values_of("out-fd").unwrap_or_default().map(parse_arg_fd).collect();
+    let output_fds = results?;
 
     let args: Vec<_> = matches.values_of("args").unwrap().map(|s| s.to_string()).collect();
     let cid =
         if let Some(arg) = matches.value_of("cid") { Some(arg.parse::<u32>()?) } else { None };
     let debuggable = matches.is_present("debug");
 
-    Ok(Config {
-        args,
-        metadata: Metadata { input_fd_annotations, output_fd_annotations },
-        cid,
-        debuggable,
-    })
+    Ok(Config { args, fd_annotation: FdAnnotation { input_fds, output_fds }, cid, debuggable })
 }
 
 fn main() -> Result<()> {
@@ -175,10 +155,10 @@
     );
 
     // 1. Parse the command line arguments for collect execution data.
-    let Config { args, metadata, cid, debuggable } = parse_args()?;
+    let Config { args, fd_annotation, cid, debuggable } = parse_args()?;
 
     // 2. Spawn and configure a fd_server to serve remote read/write requests.
-    let fd_server_jail = spawn_fd_server(&metadata, debuggable)?;
+    let fd_server_jail = spawn_fd_server(&fd_annotation, debuggable)?;
     let fd_server_lifetime = scopeguard::guard(fd_server_jail, |fd_server_jail| {
         if let Err(e) = fd_server_jail.kill() {
             if !matches!(e, minijail::Error::Killed(_)) {
@@ -189,7 +169,7 @@
 
     // 3. Send the command line args to the remote to execute.
     let service = if let Some(cid) = cid { get_rpc_binder(cid) } else { get_local_service() }?;
-    let result = service.compile(&args, &metadata).context("Binder call failed")?;
+    let result = service.compile(&args, &fd_annotation).context("Binder call failed")?;
 
     // TODO: store/use the signature
     debug!(