diff --git a/README.md b/README.md
index f2c9e75..f2af92f 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@
 
 ![Build](https://github.com/zhaofengli/colmena/workflows/Build/badge.svg)
 
-Colmena is a simple, stateless NixOS deployment tool modeled after [NixOps](https://github.com/NixOS/nixops) and [Morph](https://github.com/DBCDK/morph), written in Rust.
+Colmena is a simple, stateless [NixOS](https://nixos.org) deployment tool modeled after [NixOps](https://github.com/NixOS/nixops) and [Morph](https://github.com/DBCDK/morph), written in Rust.
 It's a thin wrapper over Nix commands like `nix-instantiate` and `nix-copy-closure`, and supports parallel deployment.
 
 <pre>
diff --git a/src/command/introspect.rs b/src/command/introspect.rs
index f0595b9..cf00d1a 100644
--- a/src/command/introspect.rs
+++ b/src/command/introspect.rs
@@ -6,8 +6,10 @@ use crate::util;
 
 pub fn subcommand() -> App<'static, 'static> {
     SubCommand::with_name("introspect")
-        .about("Evaluate expressions using the complete configuration.")
-        .long_about(r#"Your expression should take an attribute set with keys `pkgs`, `lib` and `nodes` (like a NixOS module) and return a JSON-serializable value.
+        .about("Evaluate expressions using the complete configuration")
+        .long_about(r#"Evaluate expressions using the complete configuration
+
+Your expression should take an attribute set with keys `pkgs`, `lib` and `nodes` (like a NixOS module) and return a JSON-serializable value.
 
 For example, to retrieve the configuration of one node, you may write something like:
 
@@ -15,10 +17,12 @@ For example, to retrieve the configuration of one node, you may write something
 "#)
         .arg(Arg::with_name("expression_file")
             .index(1)
+            .value_name("FILE")
             .help("The .nix file containing the expression")
             .takes_value(true))
         .arg(Arg::with_name("expression")
             .short("E")
+            .value_name("EXPRESSION")
             .help("The Nix expression")
             .takes_value(true))
 }
@@ -27,7 +31,7 @@ pub async fn run(_global_args: &ArgMatches<'_>, local_args: &ArgMatches<'_>) {
     let hive = util::hive_from_args(local_args).unwrap();
 
     if !(local_args.is_present("expression") ^ local_args.is_present("expression_file")) {
-        log::error!("Either an expression (-E) xor a .nix file containing an expression should be specified, not both.");
+        log::error!("Either an expression (-E) or a .nix file containing an expression should be specified, not both.");
         quit::with_code(1);
     }
 
diff --git a/src/main.rs b/src/main.rs
index e644617..35c19d5 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -79,6 +79,7 @@ For a sample configuration, see <https://github.com/zhaofengli/colmena>.
     command!(exec, matches);
 
     app.print_long_help().unwrap();
+    println!();
 }
 
 fn init_logging() {