Add warnings about special quota limitation scenarios (#544)

content/v2.markdown

@@ -391,7 +391,7 @@ List all domains in the account `1010` sorting them by expiration date (asc) and
 
 There is a limit to the number of requests that you can perform per hour.
 
-- For **authenticated requests** you can make **up to 2400 requests per hour**.
+- For **authenticated requests**, you can make **up to 2400 requests per hour**.
 - For **unauthenticated requests**, you can make **up to 30 requests per hour**.
 
 You can see your current rate limit status by checking the HTTP headers of any API request:
@@ -416,7 +416,7 @@ The headers have all the information you need to know about your current rate li
 | `X-RateLimit-Remaining` | The number of requests remaining in the current rate limit window. |
 | `X-RateLimit-Reset` | The time at which the current rate limit window in [Unix time](https://en.wikipedia.org/wiki/Unix_time) format. |
 
-Once you go over the rate limit you will receive an error response:
+Once you go over the rate limit, you will receive an error response:
 
 ~~~
 $ curl -H "Authorization: Bearer ACCESS-TOKEN" -I "https://api.dnsimple.com/v2/whoami"
@@ -431,6 +431,9 @@ Content-Length: 28
 {"message":"quota exceeded"}
 ~~~
 
+<warning>
+Individual API endpoints may have additional mechanisms in place to prevent abuse.
+</warning>
 
 ## More Examples
 

content/v2/registrar.markdown

@@ -11,6 +11,10 @@ excerpt: This page documents the DNSimple registry/registrar API v2.
 
 ## Check domain {#checkDomain}
 
+<warning>
+This API endpoint has stricter limits in place to avoid a high volume of requests. This endpoint should be used only to check a domain's state before issuing a domain registration or a domain transfer. For other use cases, we recommend using other services like [Domainr](https://domainr.com/).
+</warning>
+
 Checks a domain name for availability.
 
 ~~~