diff --git a/Dockerfile b/Dockerfile
index 636a8cb..5ab16d2 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -61,6 +61,11 @@ RUN npm prune --omit=dev
 # modules. The builder copies this directory whole into a compiled bundle (novox/hq ADR 0188 §5),
 # so a bundle unpacked on a machine starts — a `.js` without that package.json is read as
 # CommonJS, and an import of `nats` without node_modules beside it resolves to nothing.
+#
+# **The client libraries a catalogue module depends on are here too** (novox/hq issue 385): pg, mongodb and
+# mssql, development dependencies of node-tools, so the runtime stage prunes them. A catalogue's
+# merge-check-typescript.sh fetches nothing and copies this image's node_modules beside a module; a module
+# depending on a package that is not here cannot be type-checked or tested, and fails its check.
 FROM compiling AS toolchain
 COPY --from=lean /app/node_modules /app/runtime/node_modules
 RUN printf '{"type":"module","private":true}\n' > /app/runtime/package.json
diff --git a/node-tools/package.json b/node-tools/package.json
index 0019ab2..9bc65fa 100644
--- a/node-tools/package.json
+++ b/node-tools/package.json
@@ -19,6 +19,9 @@
   "devDependencies": {
     "@types/node": "^22.20.1",
     "typescript": "^5.9.3",
-    "esbuild": "^0.25.0"
+    "esbuild": "^0.25.0",
+    "mongodb": "^6.21.0",
+    "mssql": "^11.0.2",
+    "pg": "^8"
   }
 }