diff --git a/AGENTS.md b/AGENTS.md
index 8a3e5b4..c6c2517 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -58,6 +58,15 @@ Two types of functions:
 - Use JSON tags for TypeScript type definitions
 - Async functions automatically generate `Promise<R>` return types
 
+### Calling Convention
+
+**Important**: Functions have different calling conventions on Go vs JavaScript sides:
+
+- **Go side**: Function receives a **single argument struct** with all parameters
+- **JavaScript side**: Function is called with **individual arguments** matching the struct fields (in field order)
+
+Fields are ordered by their position in the struct, with the generated TypeScript signature using those field names as argument names.
+
 ### Example
 
 ```go
diff --git a/README.md b/README.md
index eb938e1..ba5e5e8 100644
--- a/README.md
+++ b/README.md
@@ -102,11 +102,37 @@ That's it! The framework automatically:
 - Generates TypeScript definitions
 - Manages the qjs integration
 
+### Calling Convention
+
+**Important**: There's an important difference between how functions are defined in Go versus how they're called in JavaScript:
+
+- **Go side**: The function receives a **single argument struct** containing all parameters
+- **JavaScript side**: The function is called with the **struct fields as individual arguments** (in the order they appear in the struct)
+
+```go
+// Go: Single struct argument
+type AddArgs struct {
+    A int `json:"a"`
+    B int `json:"b"`
+}
+
+func Add(_ context.Context, args AddArgs) (int, error) {
+    return args.A + args.B, nil
+}
+```
+
+```typescript
+// JavaScript: Individual arguments (not an object!)
+const result = add(5, 10);  // NOT add({ a: 5, b: 10 })
+```
+
+The framework extracts the JSON tags from the struct fields and uses them to generate the correct TypeScript function signature.
+
 ### Example
 
 ```typescript
-// TypeScript code
-const response = fetch({input: "https://httpbin.org/get"});
+// TypeScript code - call with individual arguments matching struct fields
+const response = fetch("https://httpbin.org/get");
 console.log("OK:", response.ok);
 console.log("Status:", response.status);
 console.log("Body:", response.body);
diff --git a/internal/runtime/runtime_test.go b/internal/runtime/runtime_test.go
index 0caac4d..f78b045 100644
--- a/internal/runtime/runtime_test.go
+++ b/internal/runtime/runtime_test.go
@@ -9,6 +9,7 @@ import (
 
 	"github.com/fastschema/qjs"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 
 	"reichard.io/poiesis/internal/functions"
 )
@@ -86,17 +87,14 @@ func TestAsyncFunctionResolution(t *testing.T) {
 	})
 
 	r, err := New(context.Background())
-	assert.NoError(t, err)
+	require.NoError(t, err)
 
-	result, err := r.ctx.Eval("test.js", qjs.Code(`(async () => { return await resolveTest({field1: "hello"}); })()`))
-	if err == nil && result != nil {
-		defer result.Free()
-		val, err := result.Await()
-		assert.NoError(t, err)
-		assert.Equal(t, "test-result", val.String())
-	} else {
-		t.Logf("Skipping async test - error: %v", err)
-	}
+	// Async functions need to be awaited in an async context
+	result, err := r.ctx.Eval("test.js", qjs.Code(`async function run() { return await resolveTest("hello"); }; run()`))
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	defer result.Free()
+	assert.Equal(t, "test-result", result.String())
 }
 
 func TestAsyncFunctionRejection(t *testing.T) {
@@ -105,9 +103,10 @@ func TestAsyncFunctionRejection(t *testing.T) {
 	})
 
 	r, err := New(context.Background())
-	assert.NoError(t, err)
+	require.NoError(t, err)
 
-	_, err = r.ctx.Eval("test.js", qjs.Code(`(async () => { return await rejectTest({field1: "hello"}); })()`))
+	// Rejected promises throw when awaited
+	_, err = r.ctx.Eval("test.js", qjs.Code(`async function run() { return await rejectTest("hello"); }; run()`))
 	assert.Error(t, err)
 }
 
diff --git a/internal/stdlib/fetch_test.go b/internal/stdlib/fetch_test.go
index 931d3c7..7d009f4 100644
--- a/internal/stdlib/fetch_test.go
+++ b/internal/stdlib/fetch_test.go
@@ -32,10 +32,15 @@ func TestFetch(t *testing.T) {
 }
 
 func TestFetchHTTPBin(t *testing.T) {
-	t.Skip("httpbin.org test is flaky")
 	ctx := context.Background()
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write([]byte(`{"args":{}}`))
+	}))
+	defer server.Close()
 
-	result, err := Fetch(ctx, FetchArgs{Input: "https://httpbin.org/get"})
+	result, err := Fetch(ctx, FetchArgs{Input: server.URL})
 	require.NoError(t, err)
 
 	assert.True(t, result.OK)