diff --git a/cli/src/cli/complete_word.rs b/cli/src/cli/complete_word.rs
index 827d3e6..e595ff7 100644
--- a/cli/src/cli/complete_word.rs
+++ b/cli/src/cli/complete_word.rs
@@ -72,7 +72,7 @@ impl CompleteWord {
             ctx.insert("PREV", &(cword - 1));
         }
 
-        let parsed = usage::parse::parse(spec, &words)?;
+        let parsed = usage::parse::parse_partial(spec, &words)?;
         debug!("parsed cmd: {}", parsed.cmd.full_cmd.join(" "));
         let choices = if ctoken == "-" {
             let shorts = self.complete_short_flag_names(&parsed.available_flags, "");
diff --git a/lib/src/parse.rs b/lib/src/parse.rs
index a2af1c6..82de4f3 100644
--- a/lib/src/parse.rs
+++ b/lib/src/parse.rs
@@ -15,6 +15,7 @@ pub struct ParseOutput {
     pub flags: IndexMap<SpecFlag, ParseValue>,
     pub available_flags: BTreeMap<String, SpecFlag>,
     pub flag_awaiting_value: Option<SpecFlag>,
+    pub errors: Vec<String>,
 }
 
 #[derive(Debug, EnumTryAs)]
@@ -26,6 +27,14 @@ pub enum ParseValue {
 }
 
 pub fn parse(spec: &Spec, input: &[String]) -> Result<ParseOutput, miette::Error> {
+    let out = parse_partial(spec, input)?;
+    if !out.errors.is_empty() {
+        bail!("{}", out.errors.join("\n"));
+    }
+    Ok(out)
+}
+
+pub fn parse_partial(spec: &Spec, input: &[String]) -> Result<ParseOutput, miette::Error> {
     let mut input = input.iter().cloned().collect::<VecDeque<_>>();
     input.pop_front();
 
@@ -54,6 +63,7 @@ pub fn parse(spec: &Spec, input: &[String]) -> Result<ParseOutput, miette::Error
         flags: IndexMap::new(),
         available_flags: gather_flags(&spec.cmd),
         flag_awaiting_value: None,
+        errors: vec![],
     };
 
     while !input.is_empty() {
@@ -190,6 +200,22 @@ pub fn parse(spec: &Spec, input: &[String]) -> Result<ParseOutput, miette::Error
         bail!("unexpected word: {w}");
     }
 
+    for arg in out.cmd.args.iter().skip(out.args.len()) {
+        if arg.required {
+            out.errors
+                .push(format!("missing required arg <{}>", arg.name));
+        }
+    }
+
+    for flag in out.available_flags.values() {
+        if flag.required && !out.flags.contains_key(flag) {
+            out.errors.push(format!(
+                "missing required option --{} <{}>",
+                flag.name, flag.name
+            ));
+        }
+    }
+
     Ok(out)
 }
 
diff --git a/lib/tests/parse.rs b/lib/tests/parse.rs
index 3bf5621..09f6fe6 100644
--- a/lib/tests/parse.rs
+++ b/lib/tests/parse.rs
@@ -20,6 +20,16 @@ macro_rules! tests {
 }
 
 tests! {
+    required_arg:
+        spec=r#"arg "<name>""#,
+        args="",
+        expected=r#"missing required arg <name>"#,
+
+    required_option:
+        spec=r#"flag "--name <name>" required=true"#,
+        args="",
+        expected=r#"missing required option --name <name>"#,
+
     negate:
         spec=r#"flag "--force" negate="--no-force""#,
         args="--no-force",