diff --git a/src/mcp_client.py b/src/mcp_client.py
index e5c9406f..7f44206c 100644
--- a/src/mcp_client.py
+++ b/src/mcp_client.py
@@ -328,38 +328,105 @@ def search_files_result(path: str, pattern: str) -> Result[str]:
   return Result(data="\n".join(lines))
  except Exception as e:
   return Result(data="", errors=[ErrorInfo(kind=ErrorKind.INTERNAL, message=str(e), source="mcp.search_files_result", original=e)])
+
+def edit_file_result(path: str, old_string: str, new_string: str, replace_all: bool = False) -> Result[str]:
+ resolved = _resolve_and_check_result(path)
+ if not resolved.ok:
+  return Result(data="", errors=resolved.errors)
+ p = resolved.data
+ if isinstance(p, NilPath):
+  return Result(data="", errors=resolved.errors)
+ if not p.exists():
+  return Result(data="", errors=[ErrorInfo(kind=ErrorKind.NOT_FOUND, message=f"file not found: {path}", source="mcp.edit_file_result")])
+ if not old_string:
+  return Result(data="", errors=[ErrorInfo(kind=ErrorKind.INVALID_INPUT, message="old_string cannot be empty", source="mcp.edit_file_result")])
+ try:
+  content = p.read_text(encoding="utf-8")
+  if old_string not in content:
+   return Result(data="", errors=[ErrorInfo(kind=ErrorKind.NOT_FOUND, message=f"old_string not found in '{path}'", source="mcp.edit_file_result")])
+  count = content.count(old_string)
+  if count > 1 and not replace_all:
+   return Result(data="", errors=[ErrorInfo(kind=ErrorKind.INVALID_INPUT, message=f"Found {count} matches for old_string in '{path}'. Use replace_all=true or provide more context to make it unique.", source="mcp.edit_file_result")])
+  if replace_all:
+   new_content = content.replace(old_string, new_string)
+   p.write_text(new_content, encoding="utf-8")
+   return Result(data=f"Successfully replaced {count} occurrences in '{path}'")
+  new_content = content.replace(old_string, new_string, 1)
+  p.write_text(new_content, encoding="utf-8")
+  return Result(data=f"Successfully replaced 1 occurrence in '{path}'")
+ except Exception as e:
+  return Result(data="", errors=[ErrorInfo(kind=ErrorKind.INTERNAL, message=str(e), source="mcp.edit_file_result", original=e)])
+
+def get_file_summary_result(path: str) -> Result[str]:
+ resolved = _resolve_and_check_result(path)
+ if not resolved.ok:
+  return Result(data="", errors=resolved.errors)
+ p = resolved.data
+ if isinstance(p, NilPath):
+  return Result(data="", errors=resolved.errors)
+ if not p.exists():
+  return Result(data="", errors=[ErrorInfo(kind=ErrorKind.NOT_FOUND, message=f"file not found: {path}", source="mcp.get_file_summary_result")])
+ if not p.is_file():
+  return Result(data="", errors=[ErrorInfo(kind=ErrorKind.INVALID_INPUT, message=f"not a file: {path}", source="mcp.get_file_summary_result")])
+ try:
+  content = p.read_text(encoding="utf-8")
+  return Result(data=summarize.summarise_file(p, content))
+ except Exception as e:
+  return Result(data="", errors=[ErrorInfo(kind=ErrorKind.INTERNAL, message=str(e), source="mcp.get_file_summary_result", original=e)])
+
+def get_file_slice_result(path: str, start_line: int, end_line: int) -> Result[str]:
+ resolved = _resolve_and_check_result(path)
+ if not resolved.ok:
+  return Result(data="", errors=resolved.errors)
+ p = resolved.data
+ if isinstance(p, NilPath):
+  return Result(data="", errors=resolved.errors)
+ if not p.exists():
+  return Result(data="", errors=[ErrorInfo(kind=ErrorKind.NOT_FOUND, message=f"file not found: {path}", source="mcp.get_file_slice_result")])
+ try:
+  lines = p.read_text(encoding="utf-8").splitlines(keepends=True)
+  start_idx = start_line - 1
+  end_idx = end_line
+  return Result(data="".join(lines[start_idx:end_idx]))
+ except Exception as e:
+  return Result(data="", errors=[ErrorInfo(kind=ErrorKind.INTERNAL, message=str(e), source="mcp.get_file_slice_result", original=e)])
+
+def set_file_slice_result(path: str, start_line: int, end_line: int, new_content: str) -> Result[str]:
+ resolved = _resolve_and_check_result(path)
+ if not resolved.ok:
+  return Result(data="", errors=resolved.errors)
+ p = resolved.data
+ if isinstance(p, NilPath):
+  return Result(data="", errors=resolved.errors)
+ if not p.exists():
+  return Result(data="", errors=[ErrorInfo(kind=ErrorKind.NOT_FOUND, message=f"file not found: {path}", source="mcp.set_file_slice_result")])
+ try:
+  lines = p.read_text(encoding="utf-8").splitlines(keepends=True)
+  start_idx = start_line - 1
+  end_idx = end_line
+  if new_content and not new_content.endswith("\n"):
+   new_content += "\n"
+  new_lines = new_content.splitlines(keepends=True) if new_content else []
+  lines[start_idx:end_idx] = new_lines
+  p.write_text("".join(lines), encoding="utf-8")
+  return Result(data=f"Successfully updated lines {start_line}-{end_line} in {path}")
+ except Exception as e:
+  return Result(data="", errors=[ErrorInfo(kind=ErrorKind.INTERNAL, message=str(e), source="mcp.set_file_slice_result", original=e)])
 #endregion: Result Variants
 
 def edit_file(path: str, old_string: str, new_string: str, replace_all: bool = False) -> str:
  """
  Replace exact string match in a file. Preserves indentation and line endings.
  Drop-in replacement for native edit tool that destroys 1-space indentation.
+
+ Thin wrapper over edit_file_result; the legacy str shape is preserved
+ for backward compatibility, but the try/except Exception lives in
+ the Result variant.
  """
- p, err = _resolve_and_check(path)
- if err:
-  return err
- assert p is not None
- if not p.exists():
-  return f"ERROR: file not found: {path}"
- if not old_string:
-  return "ERROR: old_string cannot be empty"
- try:
-  content = p.read_text(encoding="utf-8")
-  if old_string not in content:
-   return f"ERROR: old_string not found in '{path}'"
-  count = content.count(old_string)
-  if count > 1 and not replace_all:
-   return f"ERROR: Found {count} matches for old_string in '{path}'. Use replace_all=true or provide more context to make it unique."
-  if replace_all:
-   new_content = content.replace(old_string, new_string)
-   p.write_text(new_content, encoding="utf-8")
-   return f"Successfully replaced {count} occurrences in '{path}'"
-  else:
-   new_content = content.replace(old_string, new_string, 1)
-   p.write_text(new_content, encoding="utf-8")
-   return f"Successfully replaced 1 occurrence in '{path}'"
- except Exception as e:
-  return f"ERROR editing '{path}': {e}"
+ resolved = edit_file_result(path, old_string, new_string, replace_all)
+ if resolved.ok:
+  return resolved.data
+ return "; ".join(e.ui_message() for e in resolved.errors)
 
 def get_file_summary(path: str) -> str:
  """