diff --git a/crates/aura-std/src/sim_broker.rs b/crates/aura-std/src/sim_broker.rs
index 837e49d..422f8af 100644
--- a/crates/aura-std/src/sim_broker.rs
+++ b/crates/aura-std/src/sim_broker.rs
@@ -9,6 +9,30 @@ use aura_core::{Ctx, FieldSpec, Firing, InputSpec, Node, NodeSchema, Scalar, Sca
 /// Integrates `exposure * price-return` into cumulative pips. `pip_size` is
 /// per-instrument reference metadata (beside the hot path, C7/C15), held here,
 /// never streamed.
+///
+/// # Input slots
+///
+/// Two `f64` inputs, **order is load-bearing** (both are `f64`, so a swapped
+/// wiring is *not* caught at bootstrap — it would silently produce a wrong
+/// equity curve):
+///
+/// - **slot 0 — exposure** ∈ [-1, +1] (the strategy's intent, e.g. from
+///   [`Exposure`](crate::Exposure)).
+/// - **slot 1 — price** (the instrument price the exposure is marked against).
+///
+/// # Firing and warm-up
+///
+/// Both inputs are [`Firing::Any`](aura_core::Firing::Any), so the broker fires
+/// on **every price-fresh cycle** (price is typically the source tick). A
+/// not-yet-warmed exposure leg is read as flat `0.0`, so the broker emits an
+/// equity row from the **first** price tick, reading `0.0` until the exposure
+/// leg produces its first value — the recorded curve therefore has one row per
+/// price cycle, with leading `0.0`s during warm-up, not one row per exposure.
+///
+/// # Output
+///
+/// One `f64` column, the cumulative pip equity (a producer; tap it with a
+/// recording sink to persist the curve).
 pub struct SimBroker {
     pip_size: f64,
     prev_price: Option<f64>,