diff --git a/main.go b/main.go
index 522ae16..5310c50 100644
--- a/main.go
+++ b/main.go
@@ -6,6 +6,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"os"
+	"path"
 	"path/filepath"
 	"strings"
 
@@ -23,7 +24,7 @@ func main() {
 		}
 		return scanner.Text(), true
 	}
-	tools := []ToolDefinition{ReadFileDefinition, ListFilesDefinition}
+	tools := []ToolDefinition{ReadFileDefinition, ListFilesDefinition, EditFileDefinition}
 
 	agent := NewAgent(&client, getUserMessage, tools)
 	err := agent.Run(context.TODO())
@@ -245,3 +246,74 @@ func ListFiles(input json.RawMessage) (string, error) {
 
 	return string(result), nil
 }
+
+var EditFileDefinition = ToolDefinition{
+	Name: "edit_file",
+	Description: `Make edits to a text file.
+
+Replaces 'old_str' with 'new_str' in the given file. 'old_str' and 'new_str' MUST be different from each other.
+
+If the file specified with path doesn't exist, it will be created.
+`,
+	InputSchema: EditFileInputSchema,
+	Function:    EditFile,
+}
+
+type EditFileInput struct {
+	Path   string `json:"path" jsonschema_description:"The path to the file"`
+	OldStr string `json:"old_str" jsonschema_description:"Text to search for - must match exactly and must only have one match exactly"`
+	NewStr string `json:"new_str" jsonschema_description:"Text to replace old_str with"`
+}
+
+var EditFileInputSchema = GenerateSchema[EditFileInput]()
+
+func EditFile(input json.RawMessage) (string, error) {
+	editFileInput := EditFileInput{}
+	err := json.Unmarshal(input, &editFileInput)
+	if err != nil {
+		return "", err
+	}
+
+	if editFileInput.Path == "" || editFileInput.OldStr == editFileInput.NewStr {
+		return "", fmt.Errorf("invalid input parameters")
+	}
+
+	content, err := os.ReadFile(editFileInput.Path)
+	if err != nil {
+		if os.IsNotExist(err) && editFileInput.OldStr == "" {
+			return createNewFile(editFileInput.Path, editFileInput.NewStr)
+		}
+		return "", err
+	}
+
+	oldContent := string(content)
+	newContent := strings.Replace(oldContent, editFileInput.OldStr, editFileInput.NewStr, -1)
+
+	if oldContent == newContent && editFileInput.OldStr != "" {
+		return "", fmt.Errorf("old_str not found in file")
+	}
+
+	err = os.WriteFile(editFileInput.Path, []byte(newContent), 0644)
+	if err != nil {
+		return "", err
+	}
+
+	return "OK", nil
+}
+
+func createNewFile(filePath, content string) (string, error) {
+	dir := path.Dir(filePath)
+	if dir != "." {
+		err := os.MkdirAll(dir, 0755)
+		if err != nil {
+			return "", fmt.Errorf("failed to create directory: %w", err)
+		}
+	}
+
+	err := os.WriteFile(filePath, []byte(content), 0644)
+	if err != nil {
+		return "", fmt.Errorf("failed to create file: %w", err)
+	}
+
+	return fmt.Sprintf("Successfully created file %s", filePath), nil
+}