Add warning about MCP server default arguments (#152)

Signed-off-by: Dan Barr <[email protected]>
Co-authored-by: Dan Barr <[email protected]>

Author: danbarr

docs/toolhive/guides-cli/run-mcp-servers.mdx

@@ -150,6 +150,24 @@ thv run my-mcp-server:latest -- --arg1 value1 --arg2 value2
 
 Check the MCP server's documentation for the required arguments.
 
+:::warning
+
+Some MCP servers in the ToolHive registry include default arguments that are
+essential for proper operation. When you provide custom arguments using
+`-- <ARGS>`, these replace the registry defaults entirely rather than adding to
+them.
+
+Before adding custom arguments, check the server's registry entry:
+
+```bash
+thv registry info <SERVER> --format json | jq '.args'
+```
+
+If default arguments are listed, include them along with your custom arguments
+to ensure the server functions correctly.
+
+:::
+
 ### Run a server on a specific port
 
 ToolHive creates a reverse proxy on a random port that forwards requests to the