Fix search_source: pass env vars via mcp.json interpolation, search Plugins/, cap at 40 total lines

- .mcp.json: pass UE_ENGINE_ROOT and UE_DOCS_PATH via ${VAR} interpolation so the
  MCP server subprocess inherits them without hardcoding paths
- search_source: search both Engine/Source/ and Engine/Plugins/ (path_hint applied
  under both); switch from -m 40 (per-file cap) to streaming Popen with a true
  40-line total cap; fix UE_ENGINE_ROOT to point at Engine/ not the repo root
- Update README and CLAUDE.md to reflect the above

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.mcp.json

@@ -2,7 +2,11 @@
   "mcpServers": {
     "ue-docs": {
       "command": "python",
-      "args": ["ue_mcp_server.py"]
+      "args": ["ue_mcp_server.py"],
+      "env": {
+        "UE_ENGINE_ROOT": "${UE_ENGINE_ROOT}",
+        "UE_DOCS_PATH": "${UE_DOCS_PATH}"
+      }
     }
   }
 }

CLAUDE.md

@@ -38,9 +38,11 @@ The last argument is always the output directory. All preceding arguments are in
 | `get_class_overview(class_name)` | Compact view: description + inherits + property/function name lists |
 | `get_member(class_name, member_name)` | Full doc for one function or property (all overloads) |
 | `get_file(relative_path)` | Full `.md` file — use when you need delegates, enums, or multiple classes |
-| `search_source(pattern, path_hint)` | Grep UE source `.h` files via `$UE_ENGINE_ROOT` |
+| `search_source(pattern, path_hint)` | Grep UE `.h` files in `Engine/Source/` and `Engine/Plugins/`; `path_hint` applied under both; returns up to 40 lines total |
 
-Requires `pip install mcp`. Reads `$UE_DOCS_PATH`; `search_source` also requires `$UE_ENGINE_ROOT`.
+Requires `pip install mcp`. Reads `$UE_DOCS_PATH`; `search_source` also requires `$UE_ENGINE_ROOT` (must point to the `Engine/` directory, e.g. `/path/to/UnrealEngine/Engine`).
+
+`.mcp.json` passes both vars via `${VAR}` interpolation — no paths hardcoded.
 
 Typical query flow: `search_types` → `get_class_overview` → `get_member` (~3 calls, ~15 lines vs ~100 lines for a full file read).
 

README.md

@@ -34,10 +34,10 @@ pip install mcp
 
 ```bash
 export UE_DOCS_PATH=/path/to/your/generated/docs
-export UE_ENGINE_ROOT=/path/to/UnrealEngine   # optional, for search_source
+export UE_ENGINE_ROOT=/path/to/UnrealEngine/Engine   # optional, for search_source
 ```
 
-The `.mcp.json` at the repo root registers the server automatically when you open the project in Claude Code.
+The `.mcp.json` at the repo root registers the server automatically when you open the project in Claude Code. It reads `UE_DOCS_PATH` and `UE_ENGINE_ROOT` from your environment via `${VAR}` interpolation — no paths are hardcoded.
 
 ### Available tools
 
@@ -47,7 +47,7 @@ The `.mcp.json` at the repo root registers the server automatically when you ope
 | `get_class_overview(class_name)` | Description + base classes + property/function name lists |
 | `get_member(class_name, member_name)` | Full doc for one function or property (all overloads) |
 | `get_file(relative_path)` | Full `.md` file — for delegates, enums, or multiple classes |
-| `search_source(pattern, path_hint)` | Grep UE source `.h` files via `$UE_ENGINE_ROOT` |
+| `search_source(pattern, path_hint)` | Grep UE `.h` files in `Engine/Source/` and `Engine/Plugins/`; returns up to 40 lines |
 
 ### Typical query flow
 

ue_mcp_server.py

@@ -207,15 +207,26 @@ def get_file(relative_path: str) -> str:
 def search_source(pattern: str, path_hint: str = "") -> str:
     """Grep UE source .h files for pattern. Requires $UE_ENGINE_ROOT.
     path_hint: optional subdirectory under Engine/Source/ (e.g. 'Runtime/Engine').
+    Searches both Engine/Source/ and Engine/Plugins/.
     Returns up to 40 matching lines with file:line context."""
-    root = _engine_root() / "Engine" / "Source"
-    if path_hint:
-        root = root / path_hint
-    result = subprocess.run(
-        ["grep", "-rn", "--include=*.h", "-m", "40", pattern, str(root)],
-        capture_output=True, text=True, timeout=15
+    engine = _engine_root()
+    candidates = [engine / "Source", engine / "Plugins"]
+    search_dirs = [d / path_hint if path_hint else d for d in candidates]
+    search_dirs = [d for d in search_dirs if d.exists()]
+    if not search_dirs:
+        return "(no matches)"
+    grep = subprocess.Popen(
+        ["grep", "-rn", "--include=*.h", pattern, *map(str, search_dirs)],
+        stdout=subprocess.PIPE, stderr=subprocess.DEVNULL, text=True
     )
-    return result.stdout or "(no matches)"
+    lines = []
+    for line in grep.stdout:
+        lines.append(line)
+        if len(lines) == 40:
+            grep.kill()
+            break
+    grep.wait()
+    return "".join(lines) or "(no matches)"
 
 
 if __name__ == "__main__":