diff --git a/pkg/cli/functions.go b/pkg/cli/functions.go
index ef688fd..dcbe241 100644
--- a/pkg/cli/functions.go
+++ b/pkg/cli/functions.go
@@ -179,16 +179,16 @@ var AvailableTools = map[string]AvailableTool{
 						Type:        "string",
 						Description: "Path of the file to be modified, relative to the current working directory.",
 					},
-					"start_line": {
+					"position": {
 						Type:        "integer",
-						Description: `Which line to begin inserting lines at (existing line will be moved to after content).`,
+						Description: `Which line to insert content *before*.`,
 					},
 					"content": {
 						Type:        "string",
 						Description: `The content to insert.`,
 					},
 				},
-				Required: []string{"path", "start", "content"},
+				Required: []string{"path", "position", "content"},
 			},
 		}},
 		Impl: func(args map[string]interface{}) (string, error) {
@@ -200,14 +200,14 @@ var AvailableTools = map[string]AvailableTool{
 			if !ok {
 				return "", fmt.Errorf("Invalid path in function arguments: %v", tmp)
 			}
-			var start_line int
-			tmp, ok = args["start_line"]
+			var position int
+			tmp, ok = args["position"]
 			if ok {
 				tmp, ok := tmp.(float64)
 				if !ok {
-					return "", fmt.Errorf("Invalid start_line in function arguments: %v", tmp)
+					return "", fmt.Errorf("Invalid position in function arguments: %v", tmp)
 				}
-				start_line = int(tmp)
+				position = int(tmp)
 			}
 			var content string
 			tmp, ok = args["content"]
@@ -217,7 +217,7 @@ var AvailableTools = map[string]AvailableTool{
 					return "", fmt.Errorf("Invalid content in function arguments: %v", tmp)
 				}
 			}
-			return FileInsertLines(path, start_line, content), nil
+			return FileInsertLines(path, position, content), nil
 		},
 	},
 	"file_replace_lines": {
@@ -484,7 +484,7 @@ func WriteFile(path string, content string) string {
 	return resultToJson(FunctionResult{})
 }
 
-func FileInsertLines(path string, startLine int, content string) string {
+func FileInsertLines(path string, position int, content string) string {
 	ok, res := isPathWithinCWD(path)
 	if !ok {
 		return resultToJson(*res)
@@ -503,15 +503,15 @@ func FileInsertLines(path string, startLine int, content string) string {
 		data = []byte{}
 	}
 
-	if startLine < 1 {
+	if position < 1 {
 		return resultToJson(FunctionResult{Message: "start_line cannot be less than 1"})
 	}
 
 	lines := strings.Split(string(data), "\n")
 	contentLines := strings.Split(strings.Trim(content, "\n"), "\n")
 
-	before := lines[:startLine-1]
-	after := lines[startLine-1:]
+	before := lines[:position-1]
+	after := lines[position-1:]
 	lines = append(before, append(contentLines, after...)...)
 
 	newContent := strings.Join(lines, "\n")