diff --git a/crates/i18n-scan/src/key.rs b/crates/i18n-scan/src/key.rs
index 723177a3..8e4c7118 100644
--- a/crates/i18n-scan/src/key.rs
+++ b/crates/i18n-scan/src/key.rs
@@ -13,10 +13,12 @@
 // limitations under the License.
 
 use mas_i18n::{translations::TranslationTree, Message};
+use minijinja::machinery::Span;
 
 pub struct Context {
     keys: Vec<Key>,
     func: String,
+    current_file: Option<String>,
 }
 
 impl Context {
@@ -24,9 +26,14 @@ impl Context {
         Self {
             keys: Vec::new(),
             func,
+            current_file: None,
         }
     }
 
+    pub fn set_current_file(&mut self, file: &str) {
+        self.current_file = Some(file.to_owned());
+    }
+
     pub fn record(&mut self, key: Key) {
         self.keys.push(key);
     }
@@ -39,6 +46,28 @@ impl Context {
         let mut count = 0;
         for translatable in &self.keys {
             let message = Message::from_literal(translatable.default_value());
+
+            let location = translatable.location.as_ref().map(|location| {
+                if location.span.start_line == location.span.end_line {
+                    format!(
+                        "{}:{}:{}-{}",
+                        location.file,
+                        location.span.start_line,
+                        location.span.start_col,
+                        location.span.end_col
+                    )
+                } else {
+                    format!(
+                        "{}:{}:{}-{}:{}",
+                        location.file,
+                        location.span.start_line,
+                        location.span.start_col,
+                        location.span.end_line,
+                        location.span.end_col
+                    )
+                }
+            });
+
             let key = translatable
                 .key
                 .split('.')
@@ -48,12 +77,23 @@ impl Context {
                     None
                 });
 
-            if translation_tree.set_if_not_defined(key, message) {
+            if translation_tree.set_if_not_defined(key, message, location) {
                 count += 1;
             }
         }
         count
     }
+
+    pub fn set_key_location(&self, mut key: Key, span: Span) -> Key {
+        if let Some(file) = &self.current_file {
+            key.location = Some(Location {
+                file: file.to_owned(),
+                span,
+            });
+        }
+
+        key
+    }
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -62,15 +102,26 @@ pub enum Kind {
     Plural,
 }
 
+#[derive(Debug, Clone)]
+pub struct Location {
+    file: String,
+    span: Span,
+}
+
 #[derive(Debug, Clone)]
 pub struct Key {
     kind: Kind,
     key: String,
+    location: Option<Location>,
 }
 
 impl Key {
     pub fn new(kind: Kind, key: String) -> Self {
-        Self { kind, key }
+        Self {
+            kind,
+            key,
+            location: None,
+        }
     }
 
     pub fn default_value(&self) -> String {
diff --git a/crates/i18n-scan/src/main.rs b/crates/i18n-scan/src/main.rs
index ff6dc347..23638e0d 100644
--- a/crates/i18n-scan/src/main.rs
+++ b/crates/i18n-scan/src/main.rs
@@ -82,6 +82,7 @@ fn main() {
             let template = std::fs::read_to_string(&path).expect("Failed to read template");
             match minijinja::parse(&template, relative.as_str()) {
                 Ok(ast) => {
+                    context.set_current_file(relative.as_str());
                     minijinja::find_in_stmt(&mut context, &ast).unwrap();
                 }
                 Err(err) => {
@@ -103,6 +104,7 @@ fn main() {
         let mut file = File::options()
             .write(true)
             .read(false)
+            .truncate(true)
             .open(
                 options
                     .existing
diff --git a/crates/i18n-scan/src/minijinja.rs b/crates/i18n-scan/src/minijinja.rs
index e7c1cbd4..0ea8a6cb 100644
--- a/crates/i18n-scan/src/minijinja.rs
+++ b/crates/i18n-scan/src/minijinja.rs
@@ -14,7 +14,7 @@
 
 pub use minijinja::machinery::parse;
 use minijinja::{
-    machinery::ast::{Call, Const, Expr, Macro, Stmt},
+    machinery::ast::{Call, Const, Expr, Macro, Spanned, Stmt},
     ErrorKind,
 };
 
@@ -113,7 +113,11 @@ fn find_in_macro<'a>(context: &mut Context, macro_: &'a Macro<'a>) -> Result<(),
     Ok(())
 }
 
-fn find_in_call<'a>(context: &mut Context, call: &'a Call<'a>) -> Result<(), minijinja::Error> {
+fn find_in_call<'a>(
+    context: &mut Context,
+    call: &'a Spanned<Call<'a>>,
+) -> Result<(), minijinja::Error> {
+    let span = call.span();
     if let Expr::Var(var_) = &call.expr {
         if var_.id == context.func() {
             let key = call
@@ -134,14 +138,18 @@ fn find_in_call<'a>(context: &mut Context, call: &'a Call<'a>) -> Result<(), min
                 }
             });
 
-            context.record(Key::new(
+            let key = Key::new(
                 if has_count {
                     crate::key::Kind::Plural
                 } else {
                     crate::key::Kind::Message
                 },
                 key.to_owned(),
-            ));
+            );
+
+            let key = context.set_key_location(key, span);
+
+            context.record(key);
         }
     }
 
diff --git a/crates/i18n/src/sprintf/grammar.pest b/crates/i18n/src/sprintf/grammar.pest
index 9ae353c4..4e3bd136 100644
--- a/crates/i18n/src/sprintf/grammar.pest
+++ b/crates/i18n/src/sprintf/grammar.pest
@@ -80,4 +80,4 @@ text = @{ (!start ~ ANY)+ }
 
 start = _{ "%" }
 number = @{ ASCII_NONZERO_DIGIT ~ ASCII_DIGIT* }
-ident = @{ ASCII_ALPHA ~ ASCII_ALPHANUMERIC* }
+ident = @{ (ASCII_ALPHA | "_") ~ (ASCII_ALPHANUMERIC | "_")* }
diff --git a/crates/i18n/src/translations.rs b/crates/i18n/src/translations.rs
index 16f9719c..9b4bd0ee 100644
--- a/crates/i18n/src/translations.rs
+++ b/crates/i18n/src/translations.rs
@@ -12,10 +12,17 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use std::{collections::BTreeMap, ops::Deref};
+use std::{
+    collections::{BTreeMap, BTreeSet},
+    ops::Deref,
+};
 
 use icu_plurals::PluralCategory;
-use serde::{Deserialize, Serialize};
+use serde::{
+    de::{MapAccess, Visitor},
+    ser::SerializeMap,
+    Deserialize, Deserializer, Serialize, Serializer,
+};
 
 use crate::sprintf::Message;
 
@@ -30,20 +37,137 @@ fn plural_category_as_str(category: PluralCategory) -> &'static str {
     }
 }
 
-#[derive(Debug, Clone, Serialize, Deserialize)]
-#[serde(untagged)]
-pub enum TranslationTree {
-    Message(Message),
-    Children(BTreeMap<String, TranslationTree>),
+pub type TranslationTree = Tree;
+
+#[derive(Debug, Clone, Deserialize, Default)]
+pub struct Metadata {
+    #[serde(skip)]
+    // We don't want to deserialize it, as we're resetting it every time
+    // This then generates the `context` field when serializing
+    pub context_locations: BTreeSet<String>,
+    pub description: Option<String>,
 }
 
-impl Default for TranslationTree {
-    fn default() -> Self {
-        Self::Children(BTreeMap::new())
+impl Serialize for Metadata {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        let context = self
+            .context_locations
+            .iter()
+            .map(String::as_str)
+            .collect::<Vec<&str>>()
+            .join(", ");
+
+        let mut map = serializer.serialize_map(None)?;
+
+        if !context.is_empty() {
+            map.serialize_entry("context", &context)?;
+        }
+
+        if let Some(description) = &self.description {
+            map.serialize_entry("description", description)?;
+        }
+
+        map.end()
     }
 }
 
-impl TranslationTree {
+impl Metadata {
+    fn add_location(&mut self, location: String) {
+        self.context_locations.insert(location);
+    }
+}
+
+#[derive(Debug, Clone, Default)]
+pub struct Tree {
+    inner: BTreeMap<String, Node>,
+}
+
+#[derive(Debug, Clone)]
+pub struct Node {
+    metadata: Option<Metadata>,
+    value: Value,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(untagged)]
+pub enum Value {
+    Tree(Tree),
+    Leaf(Message),
+}
+
+impl<'de> Deserialize<'de> for Tree {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        struct TreeVisitor;
+
+        impl<'de> Visitor<'de> for TreeVisitor {
+            type Value = Tree;
+
+            fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
+                formatter.write_str("map")
+            }
+
+            fn visit_map<A>(self, mut map: A) -> Result<Self::Value, A::Error>
+            where
+                A: MapAccess<'de>,
+            {
+                let mut tree: BTreeMap<String, Node> = BTreeMap::new();
+                let mut metadata_map: BTreeMap<String, Metadata> = BTreeMap::new();
+
+                while let Some(key) = map.next_key::<String>()? {
+                    if let Some(name) = key.strip_prefix('@') {
+                        let metadata = map.next_value::<Metadata>()?;
+                        metadata_map.insert(name.to_owned(), metadata);
+                    } else {
+                        let value = map.next_value::<Value>()?;
+                        tree.insert(
+                            key,
+                            Node {
+                                metadata: None,
+                                value,
+                            },
+                        );
+                    }
+                }
+
+                for (key, meta) in metadata_map {
+                    if let Some(node) = tree.get_mut(&key) {
+                        node.metadata = Some(meta);
+                    }
+                }
+
+                Ok(Tree { inner: tree })
+            }
+        }
+
+        deserializer.deserialize_any(TreeVisitor)
+    }
+}
+
+impl Serialize for Tree {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        let mut map = serializer.serialize_map(None)?;
+
+        for (key, value) in &self.inner {
+            map.serialize_entry(key, &value.value)?;
+            if let Some(meta) = &value.metadata {
+                map.serialize_entry(&format!("@{key}"), meta)?;
+            }
+        }
+
+        map.end()
+    }
+}
+
+impl Tree {
     /// Get a message from the tree by key.
     ///
     /// Returns `None` if the requested key is not found.
@@ -51,7 +175,7 @@ impl TranslationTree {
     pub fn message(&self, key: &str) -> Option<&Message> {
         let keys = key.split('.');
         let node = self.walk_path(keys)?;
-        let message = node.as_message()?;
+        let message = node.value.as_message()?;
         Some(message)
     }
 
@@ -65,19 +189,20 @@ impl TranslationTree {
         let keys = key.split('.');
         let node = self.walk_path(keys)?;
 
-        let subtree = match node {
-            TranslationTree::Message(message) => return Some(message),
-            TranslationTree::Children(tree) => tree,
+        let subtree = match &node.value {
+            Value::Leaf(message) => return Some(message),
+            Value::Tree(tree) => tree,
         };
 
-        if let Some(node) = subtree.get(plural_category_as_str(category)) {
-            let message = node.as_message()?;
-            Some(message)
+        let node = if let Some(node) = subtree.inner.get(plural_category_as_str(category)) {
+            node
         } else {
             // Fallback to the "other" category
-            let message = subtree.get("other")?.as_message()?;
-            Some(message)
-        }
+            subtree.inner.get("other")?
+        };
+
+        let message = node.value.as_message()?;
+        Some(message)
     }
 
     #[doc(hidden)]
@@ -85,48 +210,100 @@ impl TranslationTree {
         &mut self,
         path: I,
         value: Message,
+        location: Option<String>,
     ) -> bool {
-        let mut path = path.into_iter();
-        let Some(next) = path.next() else {
-            if let TranslationTree::Message(_) = self {
-                return false;
-            }
-
-            *self = TranslationTree::Message(value);
-            return true;
+        // We're temporarily moving the tree out of the struct to be able to nicely
+        // iterate on it
+        let mut fake_root = Node {
+            metadata: None,
+            value: Value::Tree(Tree {
+                inner: std::mem::take(&mut self.inner),
+            }),
         };
 
-        match self {
-            TranslationTree::Message(_) => panic!("cannot set a value on a message node"),
-            TranslationTree::Children(children) => children
-                .entry(next.deref().to_owned())
-                .or_default()
-                .set_if_not_defined(path, value),
+        let mut node = &mut fake_root;
+        for key in path {
+            match &mut node.value {
+                Value::Tree(tree) => {
+                    node = tree.inner.entry(key.deref().to_owned()).or_insert(Node {
+                        metadata: None,
+                        value: Value::Tree(Tree::default()),
+                    });
+                }
+                Value::Leaf(_) => {
+                    panic!()
+                }
+            }
         }
+
+        let replaced = match &node.value {
+            Value::Tree(tree) => {
+                assert!(
+                    tree.inner.is_empty(),
+                    "Trying to overwrite a non-empty tree"
+                );
+
+                node.value = Value::Leaf(value);
+                true
+            }
+            Value::Leaf(_) => {
+                // Do not overwrite existing values
+                false
+            }
+        };
+
+        if let Some(location) = location {
+            node.metadata
+                .get_or_insert(Metadata::default())
+                .add_location(location);
+        }
+
+        // Restore the original tree at the end of the function
+        match fake_root {
+            Node {
+                value: Value::Tree(tree),
+                ..
+            } => self.inner = tree.inner,
+            _ => panic!("Tried to replace the root node"),
+        };
+
+        replaced
     }
 
     fn walk_path<K: Deref<Target = str>, I: IntoIterator<Item = K>>(
         &self,
         path: I,
-    ) -> Option<&TranslationTree> {
-        let mut path = path.into_iter();
-        let Some(next) = path.next() else {
-            return Some(self);
+    ) -> Option<&Node> {
+        let mut iterator = path.into_iter();
+        let Some(next) = iterator.next() else {
+            return None;
         };
 
-        match self {
-            TranslationTree::Message(_) => None,
-            TranslationTree::Children(tree) => {
-                let child = tree.get(&*next)?;
-                child.walk_path(path)
-            }
-        }
+        self.walk_path_inner(next, iterator)
     }
 
+    fn walk_path_inner<K: Deref<Target = str>, I: Iterator<Item = K>>(
+        &self,
+        next_key: K,
+        mut path: I,
+    ) -> Option<&Node> {
+        let next = self.inner.get(next_key.deref())?;
+
+        match path.next() {
+            Some(next_key) => match &next.value {
+                Value::Tree(tree) => tree.walk_path_inner(next_key, path),
+                Value::Leaf(_) => None,
+            },
+            None => Some(next),
+        }
+    }
+}
+
+impl Value {
     fn as_message(&self) -> Option<&Message> {
         match self {
-            TranslationTree::Message(message) => Some(message),
-            TranslationTree::Children(_) => None,
+            Value::Leaf(message) => Some(message),
+            Value::Tree(_) => None,
         }
     }
 }
diff --git a/templates/pages/error.html b/templates/pages/error.html
index 219582b9..f2a6ae28 100644
--- a/templates/pages/error.html
+++ b/templates/pages/error.html
@@ -19,7 +19,7 @@ limitations under the License.
 {% block content %}
 <section class="flex-1 flex items-center justify-center">
   <div class="w-64 flex flex-col gap-2">
-    <h1 class="text-xl font-semibold">Unexpected error</h1>
+    <h1 class="text-xl font-semibold">{{ _("error.unexpected") }}</h1>
     {% if code %}
     <p class="font-semibold font-mono">
       {{ code }}
diff --git a/templates/pages/index.html b/templates/pages/index.html
index 98818e51..4f24edbc 100644
--- a/templates/pages/index.html
+++ b/templates/pages/index.html
@@ -22,8 +22,7 @@ limitations under the License.
     <div class="my-2 mx-8">
       <h1 class="my-2 text-5xl font-semibold leading-tight">{{ _("app.human_name") }}</h1>
       <p class="text-lg">
-        OpenID Connect discovery document:
-        <a class="cpd-link" data-kind="primary" href="{{ discovery_url }}">{{ discovery_url }}</a>
+        {{ _("app.technical_description", discovery_url=discovery_url) }}
       </p>
     </div>
   </section>
diff --git a/translations/en.json b/translations/en.json
index 7f6f6279..9791b923 100644
--- a/translations/en.json
+++ b/translations/en.json
@@ -1,6 +1,26 @@
 {
   "app": {
     "human_name": "Matrix Authentication Service",
-    "name": "matrix-authentication-service"
+    "@human_name": {
+      "context": "pages/index.html:23:63-82",
+      "description": "Human readable name of the application"
+    },
+    "name": "matrix-authentication-service",
+    "@name": {
+      "context": "app.html:26:14-27, base.html:32:31-44",
+      "description": "Name of the application"
+    },
+    "technical_description": "OpenID Connect discovery document: <a class=\"cpd-link\" data-kind=\"primary\" href=\"%(discovery_url)s\">%(discovery_url)s</a>",
+    "@technical_description": {
+      "context": "pages/index.html:25:11-70",
+      "description": "Introduction text displayed on the home page"
+    }
+  },
+  "error": {
+    "unexpected": "Unexpected error",
+    "@unexpected": {
+      "context": "pages/error.html:22:41-62",
+      "description": "Error message displayed when an unexpected error occurs"
+    }
   }
 }
\ No newline at end of file