diff --git a/Cargo.lock b/Cargo.lock
index 94ebd99c0..c3c518c8e 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -41,6 +41,8 @@ checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
 name = "dekoder"
 version = "0.0.1"
 dependencies = [
+ "glob",
+ "hashbrown",
  "tar",
 ]
 
@@ -92,6 +94,12 @@ dependencies = [
  "num-traits",
 ]
 
+[[package]]
+name = "glob"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d2fabcfbdc87f4758337ca535fb41a6d701b65693ce38287d856d1674551ec9b"
+
 [[package]]
 name = "hashbrown"
 version = "0.14.0"
diff --git a/crates/dekoder/Cargo.toml b/crates/dekoder/Cargo.toml
index f5c585a53..1857a048d 100644
--- a/crates/dekoder/Cargo.toml
+++ b/crates/dekoder/Cargo.toml
@@ -21,3 +21,5 @@ crate-type = ["cdylib"]
 
 [dependencies]
 tar = "0.4.41"
+hashbrown = "0.14"
+glob = "0.3.1"
diff --git a/crates/dekoder/src/lib.rs b/crates/dekoder/src/lib.rs
index 317d592a1..d4028d1c7 100644
--- a/crates/dekoder/src/lib.rs
+++ b/crates/dekoder/src/lib.rs
@@ -1,9 +1,40 @@
 //! eko output reader.
+use glob::glob;
+use hashbrown::HashMap;
 use std::fs::remove_dir_all;
 use std::fs::File;
 use std::io::BufWriter;
 use std::path::PathBuf;
 
+const HEADER_EXT: &'static str = "*.yaml";
+struct Inventory {
+    /// Working directory
+    path: PathBuf,
+    /// Available items
+    keys: HashMap<String, String>,
+}
+impl Inventory {
+    /// Load all available entries
+    pub fn load_keys(&mut self) {
+        for entry in glob(self.path.join(HEADER_EXT.to_owned()).to_str().unwrap())
+            .expect("Failed to read glob pattern")
+            .filter(|x| x.is_ok())
+        {
+            self.keys.insert(
+                (*entry.unwrap().file_name().unwrap())
+                    .to_os_string()
+                    .into_string()
+                    .unwrap(),
+                "Blub".to_string(),
+            );
+        }
+    }
+
+    pub fn has_key(&self, ep: String, ulps: f64) -> bool {
+        self.keys.values().find(|v| (*v).eq(&ep)).is_some()
+    }
+}
+
 /// EKO output
 pub struct EKO {
     /// Working directory
@@ -12,8 +43,12 @@ pub struct EKO {
     tar_path: Option<PathBuf>,
     /// allow content modifications?
     read_only: bool,
+    /// final operators
+    operators: Inventory,
 }
 
+const DIR_OPERATORS: &'static str = "operators";
+
 impl EKO {
     /// Check our working directory is safe.
     fn check(&self) -> Result<(), std::io::Error> {
@@ -81,23 +116,51 @@ impl EKO {
     pub fn set_tar_path(&mut self, tar_path: PathBuf) {
         self.tar_path = Some(tar_path.to_owned());
     }
-}
 
-/// Extract tar file from `src` to `dst`.
-pub fn extract(src: PathBuf, dst: PathBuf, read_only: bool) -> EKO {
-    let mut ar = tar::Archive::new(File::open(src.to_owned()).unwrap());
-    ar.unpack(dst.to_owned()).unwrap();
-    EKO {
-        path: dst.to_owned(),
-        tar_path: Some(src.to_owned()),
-        read_only,
+    /// Open tar from `src` to `dst` for reading.
+    pub fn read(src: PathBuf, dst: PathBuf) -> Self {
+        Self::extract(src, dst, true)
+    }
+
+    /// Open tar from `src` to `dst` for editing.
+    pub fn edit(src: PathBuf, dst: PathBuf) -> Self {
+        Self::extract(src, dst, false)
+    }
+
+    /// Extract tar file from `src` to `dst`.
+    pub fn extract(src: PathBuf, dst: PathBuf, read_only: bool) -> Self {
+        let mut ar = tar::Archive::new(File::open(src.to_owned()).unwrap());
+        ar.unpack(dst.to_owned()).unwrap();
+        let mut obj = Self::load_opened(dst, read_only);
+        obj.set_tar_path(src);
+        obj
+    }
+
+    /// Load an EKO from a directory `path` (instead of tar).
+    pub fn load_opened(path: PathBuf, read_only: bool) -> Self {
+        let mut operators = Inventory {
+            path: path.join(DIR_OPERATORS),
+            keys: HashMap::new(),
+        };
+        operators.load_keys();
+        Self {
+            path,
+            tar_path: None,
+            read_only,
+            operators,
+        }
+    }
+
+    /// Check if the operator at the evolution point `ep` is available.
+    pub fn has_operator(&self, ep: String, ulps: f64) -> bool {
+        self.operators.has_key(ep, ulps)
     }
 }
 
 mod test {
     #[test]
     fn save_as_other() {
-        use super::extract;
+        use super::EKO;
         use std::fs::{remove_dir_all, remove_file};
         use std::path::PathBuf;
         let base: PathBuf = [env!("CARGO_MANIFEST_DIR"), "tests"].iter().collect();
@@ -110,7 +173,7 @@ mod test {
             let _ = remove_dir_all(dst.to_owned());
         }
         // open
-        let mut eko = extract(src.to_owned(), dst.to_owned(), false);
+        let mut eko = EKO::edit(src.to_owned(), dst.to_owned());
         let dst_exists = dst.try_exists().is_ok_and(|x| x);
         assert!(dst_exists);
         // set a different output
@@ -131,4 +194,23 @@ mod test {
             let _ = remove_dir_all(dst.to_str().unwrap());
         }
     }
+
+    #[test]
+    fn read_keys() {
+        use super::EKO;
+        use std::fs::remove_dir_all;
+        use std::path::PathBuf;
+        let base: PathBuf = [env!("CARGO_MANIFEST_DIR"), "tests"].iter().collect();
+        let src = base.join("data").join("v0.15.tar");
+        assert!(src.try_exists().is_ok_and(|x| x));
+        let dst = base.join("target").join("v0.15");
+        // get rid of previous runs if needed
+        let dst_exists = dst.try_exists().is_ok_and(|x| x);
+        if dst_exists {
+            let _ = remove_dir_all(dst.to_owned());
+        }
+        // open
+        let eko = EKO::read(src.to_owned(), dst.to_owned());
+        assert!(eko.has_operator("Blub".to_string(), 1e-7));
+    }
 }