Update README

README.md

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 # nagios-plugin-vaultaire-throughput
-Checks if the data coming into a Vaultaire origin drops below a threshold
+
+Accesses a Vaultaire telemetry origin and checks the write throughput for
+a given origin. The check passes only when the origin has addresses, all of
+them can be read, and at least one of them has been written to in the last 10
+minutes.
+
+Running the check is straightforward:
+
+````
+$ nagios-plugin-vaultaire-throughput -b chateau-02.syd1 \
+        -c tcp://chevalier-02.syd1:6283 \
+        X14C82 \
+        894LRK
+OK: Nonzero points written for origin 894LRK | points-written=556727;0;;;
+````
+
+For detailed usage instructions use the `--help` command-line option:
+
+```
+Usage: nagios-plugin-vaultaire-throughput [-b|--broker-host BROKER-HOST]
+                                          [-c|--chevalier-uri CHEVALIER-URI]
+                                          TELEMETRY-ORIGIN CHECK-ORIGIN
+
+Available options:
+  -h,--help                Show this help text
+  -b,--broker-host BROKER-HOST
+                           Vault broker host (default: "localhost")
+  -c,--chevalier-uri CHEVALIER-URI
+                           Chevalier reader URI (default: tcp://localhost:6283)
+  TELEMETRY-ORIGIN         Origin Vaultaire telemetry is written to
+  CHECK-ORIGIN             Origin for which to check throughput
+```
+
+