diff --git a/README.md b/README.md
index debbb4b..31a6414 100644
--- a/README.md
+++ b/README.md
@@ -80,12 +80,47 @@ python examples/graphnet_demo.py --prepare-only
 python examples/train_curtain.py +experiment=prometheus_demo
 ```
 
-## 📥 Reading data
-SPINE mandates **no reader**. Provide any PyTorch `Dataset` satisfying the
-contract stated canonically in `spine/data/datamodule.py`:
-`raw[i] -> {"event_no": int, "pulses": [P, F] raw, "sensor_key": [P] int}` --
-feature columns per the task's `FeatureLayout`, sensor keys matching the
-geometry asset. A minimal SQLite reference reader ships as
-`spine.data.readers.SqliteRawDataset`; GraphNeT's `LMDBDataset` /
-`SQLiteDataset` are the recommended storage layers, adapted via
-`spine_graphnet.readers.GraphNetRawDataset`.
+## 📥 What your setup provides
+SPINE plugs into your code through four contracts. Everything else (loading
+infrastructure, splits, logging, versioning) stays yours.
+
+**1. Raw events.** Any PyTorch `Dataset` yielding
+`raw[i] -> {"event_no": int, "pulses": [P, F] float32, "sensor_key": [P] int}`
+(stated canonically in `spine/data/datamodule.py`). Pulses stay raw: the
+sampler builds its cutoffs and dt targets in detector units, and
+standardization happens later at collate. Columns follow the task's
+`FeatureLayout`, by default `(x, y, z, t, charge)`; pass a different layout
+instead of reordering your data. `sensor_key` is a unique integer identity
+per sensor carried in the data itself; single PMT detectors can use any
+stable per sensor id. Reference readers:
+`spine.data.readers.SqliteRawDataset` in core, and graphnet's
+`SQLiteDataset` / `LMDBDataset` adapted via
+`spine_graphnet.readers.GraphNetRawDataset` (see `examples/graphnet_demo.py`).
+
+**2. A geometry asset.** An `.npz` with per sensor arrays: `xyz [S, 3]` in
+the same units as the pulse coordinates, `knn_idx [S, K]` neighbours sorted
+by distance (the sampler walks it to the nearest dark sensor, so K must be
+large enough that one is always found; the full sorted list is safest), and
+one unique integer key array whose name you pass to
+`load_geometry(path, sensor_key=...)`. The reader's `sensor_key` values must
+resolve through exactly these keys; coordinate matching is deliberately not
+supported. `build_geometry_asset` in `examples/graphnet_demo.py` shows a
+build from a pulse file.
+
+**3. Selections.** SPINE owns no split: `fit` takes separate train and val
+Datasets and you keep them disjoint. Every selected event must be guaranteed
+splittable: pre filter with `spine.pretext.curtain.sampler.can_always_split`
+using the same `min_visible`/`min_future` you give the task, and float32
+times. `make_sample` raises on events that slip through rather than skipping
+them silently.
+
+**4. Feature scaling.** A `FeatureScaler` subclass (`scale_pulses` and
+`scale_positions`, both applying the same xyz factors) for your detector, or
+wrap a graphnet detector with `spine_graphnet.scaling.DetectorScaler`. If you
+fine tune in graphnet afterwards, use the standardization of the downstream
+detector so the encoder sees one feature space in both stages.
+
+Bringing your own encoder instead of DeepIce is one more contract: a
+`Backbone` with `encode(batch) -> EncodedEvent` (per token embeddings, token
+mask, CLS embedding) and an `out_dim` attribute; `batch["pulses"]` arrives as
+a jagged NJT.