diff --git a/plugins/outputs/prometheus_client/README.md b/plugins/outputs/prometheus_client/README.md
index 7d4fe09b1..9beaa062d 100644
--- a/plugins/outputs/prometheus_client/README.md
+++ b/plugins/outputs/prometheus_client/README.md
@@ -3,10 +3,9 @@
 This plugin starts a [Prometheus](https://prometheus.io/) Client, it exposes
 all metrics on `/metrics` (default) to be polled by a Prometheus server.
 
-## Configuration
+### Configuration
 
 ```toml
-# Publish all metrics to /metrics for Prometheus to scrape
 [[outputs.prometheus_client]]
   ## Address to listen on.
   listen = ":9273"
@@ -52,3 +51,9 @@ all metrics on `/metrics` (default) to be polled by a Prometheus server.
   ## Export metric collection time.
   # export_timestamp = false
 ```
+
+### Metrics
+
+Prometheus metrics are produced in the same manner as the [prometheus serializer][].
+
+[prometheus serializer]: /plugins/serializers/prometheus/README.md#Metrics
diff --git a/plugins/serializers/prometheus/README.md b/plugins/serializers/prometheus/README.md
index 9a0cdfea2..19c869ffb 100644
--- a/plugins/serializers/prometheus/README.md
+++ b/plugins/serializers/prometheus/README.md
@@ -10,7 +10,7 @@ somewhat, but not fully, mitigated by using outputs that support writing in
 "batch format".  When using histogram and summary types, it is recommended to
 use only the `prometheus_client` output.
 
-## Configuration
+### Configuration
 
 ```toml
 [[outputs.file]]
@@ -35,6 +35,19 @@ use only the `prometheus_client` output.
   data_format = "prometheus"
 ```
 
+### Metrics
+
+A Prometheus metric is created for each integer, float, boolean or unsigned
+field.  Boolean values are converted to *1.0* for true and *0.0* for false.
+
+The Prometheus metric names are produced by joining the measurement name with
+the field key.  In the special case where the measurement name is `prometheus`
+it is not included in the final metric name.
+
+Prometheus labels are produced for each tag.
+
+**Note:** String fields are ignored and do not produce Prometheus metrics.
+
 ### Example
 
 **Example Input**