diff --git a/midas/cli/commands/check.py b/midas/cli/commands/check.py
index f59c479..22f654e 100644
--- a/midas/cli/commands/check.py
+++ b/midas/cli/commands/check.py
@@ -14,7 +14,7 @@ from midas.cli.highlighter import DiagnosticsHighlighter
 from midas.cli.utils import DiagnosticPrinter
 
 
-@click.command()
+@click.command(help="Run type checker and report diagnostics")
 @click.argument("file", type=click.File("r"))
 @click.option("-t", "--types", type=click.File("r"), multiple=True)
 @click.option("-l", "--highlight", type=click.File("w"))
diff --git a/midas/cli/commands/compile.py b/midas/cli/commands/compile.py
index 7d495fc..5a410f7 100644
--- a/midas/cli/commands/compile.py
+++ b/midas/cli/commands/compile.py
@@ -3,19 +3,20 @@
 # midas compile <file.py> [--types <file.midas>] [-o <output>] [--assertions|--strict|--no-checks]
 # ```
 
+import sys
 from pathlib import Path
 from typing import TextIO
 
 import click
 
 from midas.checker.checker import TypeChecker
-from midas.checker.diagnostic import Diagnostic
+from midas.checker.diagnostic import Diagnostic, DiagnosticType
 from midas.cli.utils import DiagnosticPrinter
 from midas.generator.generator import Generator
 from midas.utils import TypedAST
 
 
-@click.command()
+@click.command(help="Compile source")
 @click.argument("file", type=click.File("r"))
 @click.option("-t", "--types", type=click.File("r"), multiple=True)
 def compile(
@@ -34,5 +35,8 @@ def compile(
     printer = DiagnosticPrinter()
     printer.print_all(diagnostics)
 
+    if any(map(lambda d: d.type == DiagnosticType.ERROR, diagnostics)):
+        sys.exit(1)
+
     generator = Generator(workdir=source_path.parent)
     generator.generate(typed_ast, source_path)
diff --git a/midas/cli/commands/format.py b/midas/cli/commands/format.py
index ce570c0..1bd3dbf 100644
--- a/midas/cli/commands/format.py
+++ b/midas/cli/commands/format.py
@@ -9,7 +9,7 @@ from midas.lexer.token import Token
 from midas.parser.midas import MidasParser
 
 
-@click.command()
+@click.command(help="Parse and pretty print a Midas file")
 @click.argument("file", type=click.File("r"))
 @click.option("-o", "--output", type=click.File("w"), default="-")
 def format(file: TextIO, output: TextIO):
diff --git a/midas/cli/commands/highlight.py b/midas/cli/commands/highlight.py
index acb05e9..cf04a8d 100644
--- a/midas/cli/commands/highlight.py
+++ b/midas/cli/commands/highlight.py
@@ -46,7 +46,10 @@ def highlight_midas(source: str, path: str) -> Highlighter:
     return highlighter
 
 
-@click.command()
+@click.command(
+    help="Parse a Python or Midas file and produce a highlighted version showing AST node types inline",
+    short_help="Parse and highlight a Python or Midas file",
+)
 @click.argument("file", type=click.File("r"))
 @click.option("-o", "--output", type=click.File("w"), default="-")
 def highlight(output: TextIO, file: TextIO):
diff --git a/midas/cli/commands/parse.py b/midas/cli/commands/parse.py
index c2a2f1a..d2f5338 100644
--- a/midas/cli/commands/parse.py
+++ b/midas/cli/commands/parse.py
@@ -45,7 +45,7 @@ def dump_midas_ast(source: str, filename: str) -> str:
     return dump
 
 
-@click.command()
+@click.command(help="Parse a Python or Midas file and pretty-print its AST")
 @click.argument("file", type=click.File("r"))
 @click.option("--raw", is_flag=True)
 def parse(file: TextIO, raw: bool):
diff --git a/midas/cli/commands/registry.py b/midas/cli/commands/registry.py
index 502be75..4e830be 100644
--- a/midas/cli/commands/registry.py
+++ b/midas/cli/commands/registry.py
@@ -12,7 +12,7 @@ from midas.checker.checker import TypeChecker
 from midas.checker.types import Type
 
 
-@click.command()
+@click.command(help="Dump types registry")
 @click.option("-t", "--types", type=click.File("r"), multiple=True)
 def dump_registry(
     types: tuple[TextIO],
diff --git a/midas/cli/commands/types.py b/midas/cli/commands/types.py
index 439611d..d17a0a8 100644
--- a/midas/cli/commands/types.py
+++ b/midas/cli/commands/types.py
@@ -14,7 +14,7 @@ from midas.cli.highlighter import DiagnosticsHighlighter
 from midas.cli.utils import DiagnosticPrinter
 
 
-@click.command()
+@click.command(help="Print typing judgements")
 @click.argument("file", type=click.File("r"))
 @click.option("-t", "--types", type=click.File("r"), multiple=True)
 @click.option("-l", "--highlight", type=click.File("w"))
diff --git a/midas/cli/commands/validate.py b/midas/cli/commands/validate.py
index 44e33bb..931c3e5 100644
--- a/midas/cli/commands/validate.py
+++ b/midas/cli/commands/validate.py
@@ -14,7 +14,7 @@ from midas.cli.highlighter import DiagnosticsHighlighter
 from midas.cli.utils import DiagnosticPrinter
 
 
-@click.command()
+@click.command(help="Validate Midas definitions")
 @click.argument("file", type=click.File("r"))
 @click.option("-l", "--highlight", type=click.File("w"))
 def validate(