diff --git a/src/common/meta/src/rpc/ddl.rs b/src/common/meta/src/rpc/ddl.rs
index 21997c7b05..ed6f78154a 100644
--- a/src/common/meta/src/rpc/ddl.rs
+++ b/src/common/meta/src/rpc/ddl.rs
@@ -1432,8 +1432,10 @@ pub struct QueryContext {
     pub timezone: String,
     pub extensions: HashMap<String, String>,
     pub channel: u8,
+    /// Maps region id -> snapshot upper bound sequence for that region.
     #[serde(default)]
     pub snapshot_seqs: HashMap<u64, u64>,
+    /// Maps region id -> minimal SST sequence allowed for that region.
     #[serde(default)]
     pub sst_min_sequences: HashMap<u64, u64>,
 }
diff --git a/src/query/src/options.rs b/src/query/src/options.rs
index 758db65f46..9b60b64759 100644
--- a/src/query/src/options.rs
+++ b/src/query/src/options.rs
@@ -60,9 +60,13 @@ pub enum FlowIncrementalMode {
 
 #[derive(Debug, Clone, PartialEq, Eq, Default)]
 pub struct FlowQueryExtensions {
+    /// Maps region id -> lower exclusive sequence bound for incremental reads.
     pub incremental_after_seqs: Option<HashMap<u64, u64>>,
+    /// Incremental read mode requested by the caller.
     pub incremental_mode: Option<FlowIncrementalMode>,
+    /// Whether the caller expects per-region watermark metadata in terminal metrics.
     pub return_region_seq: bool,
+    /// Optional sink table id used to distinguish source scans from sink reads.
     pub sink_table_id: Option<TableId>,
 }