diff --git a/Cargo.lock b/Cargo.lock
index 7cf9147..622aa2d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2,6 +2,192 @@
 # It is not intended for manual editing.
 version = 4
 
+[[package]]
+name = "anstream"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "824a212faf96e9acacdbd09febd34438f8f711fb84e09a8916013cd7815ca28d"
+dependencies = [
+ "anstyle",
+ "anstyle-parse",
+ "anstyle-query",
+ "anstyle-wincon",
+ "colorchoice",
+ "is_terminal_polyfill",
+ "utf8parse",
+]
+
+[[package]]
+name = "anstyle"
+version = "1.0.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "940b3a0ca603d1eade50a4846a2afffd5ef57a9feac2c0e2ec2e14f9ead76000"
+
+[[package]]
+name = "anstyle-parse"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "52ce7f38b242319f7cabaa6813055467063ecdc9d355bbb4ce0c68908cd8130e"
+dependencies = [
+ "utf8parse",
+]
+
+[[package]]
+name = "anstyle-query"
+version = "1.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "40c48f72fd53cd289104fc64099abca73db4166ad86ea0b4341abe65af83dadc"
+dependencies = [
+ "windows-sys",
+]
+
+[[package]]
+name = "anstyle-wincon"
+version = "3.0.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "291e6a250ff86cd4a820112fb8898808a366d8f9f58ce16d1f538353ad55747d"
+dependencies = [
+ "anstyle",
+ "once_cell_polyfill",
+ "windows-sys",
+]
+
+[[package]]
+name = "anyhow"
+version = "1.0.102"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7f202df86484c868dbad7eaa557ef785d5c66295e41b460ef922eca0723b842c"
+
+[[package]]
+name = "clap"
+version = "4.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b193af5b67834b676abd72466a96c1024e6a6ad978a1f484bd90b85c94041351"
+dependencies = [
+ "clap_builder",
+ "clap_derive",
+]
+
+[[package]]
+name = "clap_builder"
+version = "4.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "714a53001bf66416adb0e2ef5ac857140e7dc3a0c48fb28b2f10762fc4b5069f"
+dependencies = [
+ "anstream",
+ "anstyle",
+ "clap_lex",
+ "strsim",
+]
+
+[[package]]
+name = "clap_derive"
+version = "4.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1110bd8a634a1ab8cb04345d8d878267d57c3cf1b38d91b71af6686408bbca6a"
+dependencies = [
+ "heck",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "clap_lex"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c8d4a3bb8b1e0c1050499d1815f5ab16d04f0959b233085fb31653fbfc9d98f9"
+
+[[package]]
+name = "colorchoice"
+version = "1.0.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1d07550c9036bf2ae0c684c4297d503f838287c83c53686d05370d0e139ae570"
+
 [[package]]
 name = "gitea-pr-review"
 version = "0.1.0"
+dependencies = [
+ "anyhow",
+ "clap",
+]
+
+[[package]]
+name = "heck"
+version = "0.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2304e00983f87ffb38b55b444b5e3b60a884b5d30c0fca7d82fe33449bbe55ea"
+
+[[package]]
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+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a6cb138bb79a146c1bd460005623e142ef0181e3d0219cb493e02f7d08a35695"
+
+[[package]]
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+version = "1.70.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "384b8ab6d37215f3c5301a95a4accb5d64aa607f1fcb26a11b5303878451b4fe"
+
+[[package]]
+name = "proc-macro2"
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+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8fd00f0bb2e90d81d1044c2b32617f68fcb9fa3bb7640c23e9c748e53fb30934"
+dependencies = [
+ "unicode-ident",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.45"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "41f2619966050689382d2b44f664f4bc593e129785a36d6ee376ddf37259b924"
+dependencies = [
+ "proc-macro2",
+]
+
+[[package]]
+name = "strsim"
+version = "0.11.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7da8b5736845d9f2fcb837ea5d9e2628564b3b043a70948a3f0b778838c5fb4f"
+
+[[package]]
+name = "syn"
+version = "2.0.117"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e665b8803e7b1d2a727f4023456bbbbe74da67099c585258af0ad9c5013b9b99"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
+[[package]]
+name = "unicode-ident"
+version = "1.0.24"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e6e4313cd5fcd3dad5cafa179702e2b244f760991f45397d14d4ebf38247da75"
+
+[[package]]
+name = "utf8parse"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "06abde3611657adf66d383f00b093d7faecc7fa57071cce2578660c9f1010821"
+
+[[package]]
+name = "windows-link"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f0805222e57f7521d6a62e36fa9163bc891acd422f971defe97d64e70d0a4fe5"
+
+[[package]]
+name = "windows-sys"
+version = "0.61.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ae137229bcbd6cdf0f7b80a31df61766145077ddf49416a728b02cb3921ff3fc"
+dependencies = [
+ "windows-link",
+]
diff --git a/Cargo.toml b/Cargo.toml
index 24a2b8c..0c0330c 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,3 +4,5 @@ version = "0.1.0"
 edition = "2024"
 
 [dependencies]
+anyhow = "1.0"
+clap = { version = "4.5", features = ["derive"] }
diff --git a/src/cli.rs b/src/cli.rs
new file mode 100644
index 0000000..3b29805
--- /dev/null
+++ b/src/cli.rs
@@ -0,0 +1,41 @@
+use clap::{Parser, Subcommand, ValueEnum};
+use std::path::PathBuf;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, ValueEnum)]
+pub enum OutputFormat {
+    Markdown,
+    Json,
+}
+
+#[derive(Debug, Parser)]
+#[command(name = "gitea-pr-review")]
+pub struct Cli {
+    #[command(subcommand)]
+    pub command: Commands,
+}
+
+#[derive(Debug, Subcommand)]
+pub enum Commands {
+    Fetch(FetchArgs),
+    RenderMd(RenderMdArgs),
+}
+
+#[derive(Debug, clap::Args)]
+pub struct FetchArgs {
+    pub pr_index: i64,
+
+    #[arg(long, value_enum, default_value_t = OutputFormat::Markdown)]
+    pub format: OutputFormat,
+
+    #[arg(long)]
+    pub out: Option<PathBuf>,
+}
+
+#[derive(Debug, clap::Args)]
+pub struct RenderMdArgs {
+    #[arg(long = "in")]
+    pub input: PathBuf,
+
+    #[arg(long)]
+    pub out: Option<PathBuf>,
+}
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..ecbf2c1
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,5 @@
+pub mod cli;
+
+pub fn run() -> anyhow::Result<()> {
+    Ok(())
+}
diff --git a/src/main.rs b/src/main.rs
index e7a11a9..861aab2 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,3 @@
-fn main() {
-    println!("Hello, world!");
+fn main() -> anyhow::Result<()> {
+    gitea_pr_review::run()
 }
diff --git a/tests/cli_parse_tests.rs b/tests/cli_parse_tests.rs
new file mode 100644
index 0000000..508b07c
--- /dev/null
+++ b/tests/cli_parse_tests.rs
@@ -0,0 +1,34 @@
+use clap::Parser;
+use gitea_pr_review::cli::{Cli, Commands, OutputFormat};
+
+#[test]
+fn parse_fetch_default_format() {
+    let cli = Cli::try_parse_from(["gitea-pr-review", "fetch", "12"]).unwrap();
+    match cli.command {
+        Commands::Fetch(args) => {
+            assert_eq!(args.pr_index, 12);
+            assert_eq!(args.format, OutputFormat::Markdown);
+            assert!(args.out.is_none());
+        }
+        _ => panic!("expected fetch"),
+    }
+}
+
+#[test]
+fn parse_render_md_requires_input() {
+    let cli = Cli::try_parse_from([
+        "gitea-pr-review",
+        "render-md",
+        "--in",
+        "sample.json",
+    ])
+    .unwrap();
+
+    match cli.command {
+        Commands::RenderMd(args) => {
+            assert_eq!(args.input.display().to_string(), "sample.json");
+            assert!(args.out.is_none());
+        }
+        _ => panic!("expected render-md"),
+    }
+}