diff --git a/__wasm/wit-bindgen-sample/README.md b/__wasm/wit-bindgen-sample/README.md
index 7a1c4c2..f26674d 100644
--- a/__wasm/wit-bindgen-sample/README.md
+++ b/__wasm/wit-bindgen-sample/README.md
@@ -1,3 +1,12 @@
 
+Requires:
+* Rust (with target wasm32-unknown-unknown)
+
+
+Check out wit-bindgen:
+```shell
 git clone https://github.com/bytecodealliance/wit-bindgen.git
+```
+
+
 
diff --git a/__wasm/wit-bindgen-sample/container/src/fn_common.rs b/__wasm/wit-bindgen-sample/container/src/fn_common.rs
index 9b3d50b..2a0abb6 100644
--- a/__wasm/wit-bindgen-sample/container/src/fn_common.rs
+++ b/__wasm/wit-bindgen-sample/container/src/fn_common.rs
@@ -14,9 +14,9 @@ impl FnResult {
         }
     }
 
-    pub fn success(result: String) -> Self {
+    pub fn success(result: impl Into<String>) -> Self {
         FnResult {
-            result: Some(result),
+            result: Some(result.into()),
             error: None,
         }
     }
diff --git a/__wasm/wit-bindgen-sample/container/src/fn_fetch.rs b/__wasm/wit-bindgen-sample/container/src/fn_fetch.rs
index f790fdc..9babf55 100644
--- a/__wasm/wit-bindgen-sample/container/src/fn_fetch.rs
+++ b/__wasm/wit-bindgen-sample/container/src/fn_fetch.rs
@@ -96,16 +96,16 @@ pub fn do_fetch(params: &str) -> FnResult {
 
     let mut result_map = Map::new();
     result_map.insert("status".to_string(), Value::Number(Number::from(status)));
-    let mut header_map = Map::new();
+    let mut headers_map = Map::new();
     for (k, v) in headers {
         let header_key = k.map(|n| n.as_str().to_string()).unwrap_or_else(|| "".to_string());
         let header_value = match v.to_str() {
             Err(_) => continue,
             Ok(v) => v.to_string(),
         };
-        header_map.insert(header_key, Value::String(header_value));
+        headers_map.insert(header_key, Value::String(header_value));
     }
-    result_map.insert("headers".to_string(), Value::Object(header_map));
+    result_map.insert("headers".to_string(), Value::Object(headers_map));
     result_map.insert("body".to_string(), Value::String(String::from_utf8_lossy(&body_buff).to_string()));
 
     FnResult::success(format!("{}", Value::Object(result_map)))
diff --git a/__wasm/wit-bindgen-sample/container/src/main.rs b/__wasm/wit-bindgen-sample/container/src/main.rs
index 4d9b4ff..96d1bcf 100644
--- a/__wasm/wit-bindgen-sample/container/src/main.rs
+++ b/__wasm/wit-bindgen-sample/container/src/main.rs
@@ -30,15 +30,15 @@ fn main() -> Result<()> {
     )?;
     let a = exports.eval_javascript(&mut store, r##"
         function hi(name) { return "hi: " + name; }
-        let a = [];
-        a.push(fetch('https://hatter.ink/util/print_request.action'));
-        for (let i = 0; i < 3; i++) { a.push(i); }
-        a.push({
-          id: 1, name: 'hatter'
-        });
-        a.push(hi('001'));
-        a.push(hi('002'));
-        // let a = fetch('https://hatter.ink/util/print_request.action');
+        // let a = [];
+        // a.push(fetch('https://hatter.ink/util/print_request.action'));
+        // for (let i = 0; i < 3; i++) { a.push(i); }
+        // a.push({
+        //   id: 1, name: 'hatter'
+        // });
+        // a.push(hi('001'));
+        // a.push(hi('002'));
+        let a = fetch('https://hatter.ink/util/print_request.action');
         JSON.stringify(a)
         // a
     "##);
diff --git a/__wasm/wit-bindgen-sample/engine/src/lib.rs b/__wasm/wit-bindgen-sample/engine/src/lib.rs
index cc0b421..91768a6 100644
--- a/__wasm/wit-bindgen-sample/engine/src/lib.rs
+++ b/__wasm/wit-bindgen-sample/engine/src/lib.rs
@@ -9,15 +9,12 @@ struct Exports;
 impl exports::Exports for Exports {
     fn eval_javascript(script: String) -> String {
         let mut ctx = Context::default();
-        ctx.register_global_function("fetch", 0, fetch_fn);
+        ctx.register_global_function("fetch", 0, do_fetch);
         let o = match ctx.eval(&script) {
             JsResult::Ok(o) => o,
             JsResult::Err(o) => o,
         };
-        format!("{}", o.to_json(&mut ctx).unwrap())
-        // let a = container::fetch("");
-        // let a = fetch_from_host("<CONFIG>");
-        // format!("eval: {}, fetched: {}", s, a)
+        format!("{}", o.to_json(&mut ctx).expect("To JSON error"))
     }
 }
 
@@ -27,14 +24,17 @@ struct FetchResult {
     result: Option<String>,
 }
 
-fn fetch_fn(_: &JsValue, args: &[JsValue], ctx: &mut Context) -> JsResult<JsValue> {
+fn do_fetch(_: &JsValue, args: &[JsValue], ctx: &mut Context) -> JsResult<JsValue> {
+    if args.is_empty() {
+        return JsResult::Err(JsValue::String(JsString::from("Requires at least one argument")));
+    }
     let mut fetch_params_map = Map::new();
     fetch_params_map.insert("url".to_string(), args[0].to_json(ctx).expect("error"));
     if args.len() > 1 {
         fetch_params_map.insert("params".to_string(), args[1].to_json(ctx).expect("error"));
     }
     let fetch_params = format!("{}", Value::Object(fetch_params_map));
-    
+
     let fetch_result_string = container::fetch(&fetch_params);
     let fetch_result: FetchResult = serde_json::from_str(&fetch_result_string).expect("from str error");
     if let Some(result) = fetch_result.result {
@@ -42,5 +42,5 @@ fn fetch_fn(_: &JsValue, args: &[JsValue], ctx: &mut Context) -> JsResult<JsValu
         let v = JsValue::from_json(&r, ctx).unwrap();
         return JsResult::Ok(v);
     }
-    JsResult::Err(JsValue::String(JsString::from(format!("Invoke fetch error: {}", fetch_result.error.unwrap_or("".to_string())))))
+    JsResult::Err(JsValue::String(JsString::from(format!("Invoke fetch error: {}", fetch_result.error.unwrap_or("<unknown>".to_string())))))
 }
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