diff --git a/.dockerignore b/.dockerignore
new file mode 100644
index 0000000..5890b09
--- /dev/null
+++ b/.dockerignore
@@ -0,0 +1 @@
+test.py
diff --git a/.github/workflows/unit_test.yml b/.github/workflows/unit_test.yml
new file mode 100644
index 0000000..1c91a8c
--- /dev/null
+++ b/.github/workflows/unit_test.yml
@@ -0,0 +1,19 @@
+name: Python package
+
+on:
+  push:
+    branches:
+      - 'main'
+  pull_request:
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Set up Python 3.12
+        uses: actions/setup-python@v5
+        with:
+          python-version: 3.12
+      - name: Run unit tests
+        run: ./test.py
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..026bbc3
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+*.json
+__pycache__
diff --git a/Dockerfile b/Dockerfile
index 03ecbcc..fe3af3d 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,8 +1,9 @@
 FROM node:20-alpine
 
-RUN apk add --no-cache jq=1.7.1-r0 curl=8.8.0-r0 && \
+RUN apk add --no-cache curl=8.8.0-r0 python3=3.12.3-r1 && \
 	npm install -g wikibase-cli@18.0.3
 
 COPY --chmod=755 ./transferbot.sh /usr/bin/transferbot
+COPY --chmod=755 ./mangle_data.py /usr/bin/mangle_data
 
 ENTRYPOINT ["transferbot"]
diff --git a/mangle_data.py b/mangle_data.py
new file mode 100755
index 0000000..e782589
--- /dev/null
+++ b/mangle_data.py
@@ -0,0 +1,55 @@
+#!/usr/bin/env python3
+
+import argparse
+import json
+import fileinput
+from urllib import request
+
+parser = argparse.ArgumentParser(
+    description="Adjust a line from wb-cli so it can be fed into the target wiki"
+)
+
+parser.add_argument("-t", "--target", action="store", dest="target", required=True)
+parser.add_argument("-p", "--pick", action="append", dest="pick", required=True)
+
+
+def process_entity(line, pick=[], select_languages=set()):
+    out = {}
+    for key, value in line.items():
+        if key not in pick:
+            continue
+
+        if not isinstance(value, dict):
+            out[key] = value
+            continue
+
+        out[key] = {}
+        for lang, value in line[key].items():
+            if lang in select_languages:
+                out[key][lang] = value
+
+    return out
+
+
+def get_contentlanguages(target_origin):
+    with request.urlopen(
+        f"{target_origin}/w/api.php?action=query&meta=wbcontentlanguages&format=json"
+    ) as response:
+        raw_body = response.read()
+    body = json.loads(raw_body)
+    return set(body["query"]["wbcontentlanguages"].keys())
+
+
+def main():
+    args = parser.parse_args()
+    target_languages = get_contentlanguages(args.target)
+
+    for line in fileinput.input("-"):
+        out = process_entity(
+            json.loads(line), pick=args.pick, select_languages=target_languages
+        )
+        print(json.dumps(out, ensure_ascii=False))
+
+
+if __name__ == "__main__":
+    main()
diff --git a/test.py b/test.py
new file mode 100755
index 0000000..cf4598e
--- /dev/null
+++ b/test.py
@@ -0,0 +1,152 @@
+#!/usr/bin/env python3
+
+import unittest
+import urllib
+from unittest.mock import MagicMock, patch
+
+from mangle_data import process_entity, get_contentlanguages
+
+
+class TestProcessEntity(unittest.TestCase):
+    def test_empty(self):
+        result = process_entity({})
+        self.assertEqual(result, {})
+
+    def test_skip_languages(self):
+        result = process_entity(
+            {
+                "labels": {
+                    "en": {
+                        "language": "en",
+                        "value": "pipe",
+                    },
+                    "fr": {
+                        "language": "fr",
+                        "value": "pipe",
+                    },
+                    "de": {
+                        "language": "de",
+                        "value": "Pfeife",
+                    },
+                }
+            },
+            pick=["labels"],
+            select_languages=["en", "fr"],
+        )
+        self.assertEqual(
+            result,
+            {
+                "labels": {
+                    "en": {
+                        "language": "en",
+                        "value": "pipe",
+                    },
+                    "fr": {
+                        "language": "fr",
+                        "value": "pipe",
+                    },
+                }
+            },
+        )
+
+    def test_pick_keys(self):
+        result = process_entity(
+            {
+                "labels": {
+                    "en": {
+                        "language": "en",
+                        "value": "pipe",
+                    },
+                    "fr": {
+                        "language": "fr",
+                        "value": "pipe",
+                    },
+                    "de": {
+                        "language": "de",
+                        "value": "Pfeife",
+                    },
+                },
+                "other": {
+                    "en": {
+                        "language": "en",
+                        "value": "pipe",
+                    },
+                    "fr": {
+                        "language": "fr",
+                        "value": "pipe",
+                    },
+                    "de": {
+                        "language": "de",
+                        "value": "Pfeife",
+                    },
+                },
+            },
+            pick=["labels"],
+            select_languages=["en", "fr", "de"],
+        )
+        self.assertEqual(
+            result,
+            {
+                "labels": {
+                    "en": {
+                        "language": "en",
+                        "value": "pipe",
+                    },
+                    "fr": {
+                        "language": "fr",
+                        "value": "pipe",
+                    },
+                    "de": {
+                        "language": "de",
+                        "value": "Pfeife",
+                    },
+                },
+            },
+        )
+
+    def test_pick_non_dict(self):
+        result = process_entity(
+            {
+                "type": "item",
+                "labels": {
+                    "en": {
+                        "language": "en",
+                        "value": "pipe",
+                    },
+                    "fr": {
+                        "language": "fr",
+                        "value": "pipe",
+                    },
+                    "de": {
+                        "language": "de",
+                        "value": "Pfeife",
+                    },
+                },
+            },
+            pick=["type"],
+            select_languages=["en", "fr", "de"],
+        )
+        self.assertEqual(
+            result,
+            {
+                "type": "item",
+            },
+        )
+
+
+class TestGetContentlanguages(unittest.TestCase):
+    @patch("urllib.request.urlopen")
+    def test_success(self, mock_urlopen):
+        cm = MagicMock()
+        cm.read.return_value = '{"batchcomplete":"","query":{"wbcontentlanguages":{"aa":{"code":"aa"},"bb":{"code":"bb"}}}}'
+        cm.__enter__.return_value = cm
+        mock_urlopen.return_value = cm
+        with urllib.request.urlopen(
+            "https://test.wikibase.cloud/w/api.php?action=query&meta=wbcontentlanguages&format=json"
+        ):
+            result = get_contentlanguages("https://test.wikibase.cloud")
+            self.assertSetEqual(result, {"aa", "bb"})
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/transferbot.sh b/transferbot.sh
index 1048c5c..abda3b2 100644
--- a/transferbot.sh
+++ b/transferbot.sh
@@ -37,5 +37,5 @@ CREDS
 } > $(wb config path)
 
 wb data $@ --instance "$source_wiki_origin" |\
-  jq --compact-output '{type,labels,descriptions,aliases,datatype}' |\
+  mangle_data -t "$target_wiki_origin" -p type -p labels -p descriptions -p aliases -p datatype |\
   wb create-entity --batch --instance "$target_wiki_origin"