diff --git a/README.md b/README.md
index 35ddebd..25c550d 100644
--- a/README.md
+++ b/README.md
@@ -1,10 +1,14 @@
 # Perfloop relay
 
-A small program you run inside your network so Perfloop can read a
-Prometheus, VictoriaMetrics, or Loki that the public internet cannot reach.
-This repository is the complete source of what runs there. The image Perfloop
-publishes is built from it, by the workflow in this repository, and is tagged
-with the commit it was built from.
+A small program you run inside your network so Perfloop can read the
+telemetry you keep there: metrics, logs, and profiles from providers the
+public internet cannot reach. This repository is the complete source of what
+runs there. The image Perfloop publishes is built from it, by the workflow in
+this repository, and is tagged with the commit it was built from.
+
+Sources the relay reads today: Prometheus, VictoriaMetrics, and Loki. Go
+pprof and Pyroscope are next. Each kind is one table of read routes in
+`routes.go`, and a kind the relay does not know is refused when it starts.
 
 756 lines of Go outside tests, three runtime dependencies (`coder/websocket`,
 `go.yaml.in/yaml/v3`, `golang.org/x/net`): read it in an afternoon.
diff --git a/config.go b/config.go
index a8f6db0..552310c 100644
--- a/config.go
+++ b/config.go
@@ -40,7 +40,8 @@ type Upstream struct {
 	// Name is the `relay://<name>` endpoint that Setup registers. It is one
 	// lowercase DNS label.
 	Name string `yaml:"name"`
-	// Kind is prometheus, victoriametrics, or loki. It selects the read
+	// Kind selects the read routes the relay permits; routes.go lists the
+	// kinds (today prometheus, victoriametrics, and loki). It selects the read
 	// routes the relay permits.
 	Kind string `yaml:"kind"`
 	// URL is the provider base: scheme, host, port, and an optional path
diff --git a/docs/configuration.md b/docs/configuration.md
index 254e8e4..11b34f8 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -27,7 +27,8 @@ upstreams:
     # lowercase DNS label: a-z, 0-9, and -, up to 63 characters, no
     # leading or trailing -. Names must be unique in the file.
     name: vm
-    # prometheus, victoriametrics, or loki. Selects the read routes
+    # One of the kinds routes.go lists: today prometheus, victoriametrics,
+    # or loki. Selects the read routes
     # (docs/security.md, "What the relay forwards").
     kind: victoriametrics
     # The provider base: scheme, host, port, and an optional path prefix.
diff --git a/docs/setup.md b/docs/setup.md
index a0ccb05..38b3a5a 100644
--- a/docs/setup.md
+++ b/docs/setup.md
@@ -13,7 +13,7 @@ Collect these before starting. Nothing else is needed.
 | `<tenant>` | Your Perfloop tenant name, the segment after `/t/` in the app URL. |
 | `<namespace>` | The Kubernetes namespace the relay will run in. |
 | `<upstream-name>` | A name you choose for the source, one lowercase DNS label, for example `vm`. |
-| `<kind>` | `prometheus`, `victoriametrics`, or `loki`. |
+| `<kind>` | One of the kinds `routes.go` lists: today `prometheus`, `victoriametrics`, or `loki`. |
 | `<upstream-url>` | The provider base URL as reachable from inside the cluster, for example `http://vmselect.monitoring.svc:8481/select/0/prometheus`. No trailing slash. |
 | `<upstream-read-token>` | A read-only token for that upstream, if it needs one. Query-scoped. |
 | `<digest>` | The relay image digest to pin. See "Choose the image" below. |
diff --git a/examples/kubernetes/relay.yaml b/examples/kubernetes/relay.yaml
index f2609fc..a847c2a 100644
--- a/examples/kubernetes/relay.yaml
+++ b/examples/kubernetes/relay.yaml
@@ -18,7 +18,7 @@ data:
     token: ${PERFLOOP_RELAY_TOKEN}
     upstreams:
       - name: <upstream-name>
-        kind: <prometheus|victoriametrics|loki>
+        kind: <kind>   # one of the kinds routes.go lists: prometheus, victoriametrics, loki
         url: http://<upstream-service>.<upstream-namespace>.svc:<upstream-port>
         headers:
           Authorization: Bearer ${UPSTREAM_READ_TOKEN}