docs: fix OpenAPI petstore example (#233)

Signed-off-by: Grant Linville <[email protected]>

Author: g-linville

docs/docs/03-tools/03-openapi.md

@@ -7,9 +7,9 @@ GPTScript will automatically and internally generate the necessary code to make
 Here is an example that uses the OpenAPI [Petstore Example](https://github.com/OAI/OpenAPI-Specification/blob/main/examples/v3.0/petstore.yaml):
 
 ```yaml
-Tools: https://raw.githubusercontent.com/OAI/OpenAPI-Specification/main/examples/v3.0/petstore.yaml
+Tools: https://petstore.gptscript-demos.ai/openapi
 
-List all the pets. After you get a response, create a new pet named Mark. He is a lizard.
+List all the pets. What are the names of the dogs?
 ```
 
 You can also use a local file path instead of a URL.
@@ -22,6 +22,11 @@ If no HTTPS server exists, it will choose the first HTTP server. Other protocols
 GPTScript will also handle path- and operation-level server overrides, following the same logic of choosing the first HTTPS server it finds,
 or the first HTTP server if no HTTPS server exists in the array.
 
+If no servers are defined in the definition, and the definition was downloaded from a URL, GPTScript will use the host
+in the URL as the server value. This is the case with the Petstore example above.
+
+### Server Variables
+
 Additionally, GPTScript can handle variables in the server name. For example, this:
 
 ```yaml