diff --git a/crates/agent/src/tools/streaming_edit_file_tool.rs b/crates/agent/src/tools/streaming_edit_file_tool.rs
index 81846ec282a52cc694a0f1c8e8418b5202d7e0d6..c326ed3c10170d1c45517103ba02e178bec32c36 100644
--- a/crates/agent/src/tools/streaming_edit_file_tool.rs
+++ b/crates/agent/src/tools/streaming_edit_file_tool.rs
@@ -108,6 +108,11 @@ pub enum StreamingEditFileMode {
 pub struct Edit {
     /// The exact text to find in the file. This will be matched using fuzzy matching
     /// to handle minor differences in whitespace or formatting.
+    ///
+    /// Always include complete lines. Do not start or end mid-line.
+    /// Be minimal with replacements:
+    /// - For unique lines, include only those lines
+    /// - For non-unique lines, include enough context to identify them
     pub old_text: String,
     /// The text to replace it with
     pub new_text: String,