diff --git a/.github/workflows/validate-openapi.yml b/.github/workflows/validate-openapi.yml
new file mode 100644
index 0000000..4ca530c
--- /dev/null
+++ b/.github/workflows/validate-openapi.yml
@@ -0,0 +1,25 @@
+name: Validate OpenAPI spec
+
+on:
+  pull_request:
+    branches:
+      - main
+
+permissions:
+  contents: read
+
+jobs:
+  validate-spec:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+      - name: Validate JSON spec structure
+        run: |
+          python - <<'PY'
+          import json
+          from pathlib import Path
+
+          spec = json.loads(Path('openapi/spec.json').read_text())
+          assert str(spec.get('openapi', '')).startswith('3.'), 'Expected OpenAPI 3 specification'
+          assert isinstance(spec.get('paths'), dict) and spec['paths'], 'Specification has no paths'
+          PY