Improve README; check-ssl-cert
-check-ssl-cert
-==========
+# check-ssl-cert
+
+## Description
Check the ssl certification's expiry.
## Synopsis
+```
+check-ssl-cert --host mackerel.io --warning 30 --critical 7
+```
+
+## Installation
+
+First, build this program.
+
+```
+go get github.com/mackerelio/go-check-plugins
+cd $(go env GOPATH)/src/github.com/mackerelio/go-check-plugins/check-ssl-cert
+go install
+```
+
+Or you can use this program by installing the official Mackerel package. See [Using the official check plugin pack for check monitoring - Mackerel Docs](https://mackerel.io/docs/entry/howto/mackerel-check-plugins).
+
-```shell
+Next, you can execute this program :-)
+
+```
check-ssl-cert --host mackerel.io --warning 30 --critical 7
```
-## Options
+
+## Setting for mackerel-agent
+
+If there are no problems in the execution result, add s setting in mackerel-agent.conf .
+
+```
+[plugin.checks.check-ssl-cert-sample]
+command = ["check-ssl-cert", "--host", "mackerel.io", "--warning", "30", "--critical", "7"]
+```
+
+## Usage
+### Options
```
-Application Options:
-H, --host= Host name
-p, --port= Port number (default: 443)
-w, --warning=days The warning threshold in days before expiry (default: 30)
-c, --critical=days The critical threshold in days before expiry (default: 14)
```
+
+## For more information
+
+Please execute `check-ssl-cert -h` and you can get command line options.
