This feature is often requested.
https://oldschool.runescape.wiki/api.php?action=opensearch&format=json&formatversion=2&search=abyssal&namespace=0%7C302%7C308&limit=10&suggest=true
GET https://oldschool.runescape.wiki/api.php
QueryParams:
action=opensearch
search=[SEARCH QUERY HERE]
(limit=10 (default is 10, can be other values))
[
"abyssal",
[
"Abyssal",
"Abyssal whip",
"Abyssal Sire",
...
],
[
"",
"",
"",
...
],
[
"https://oldschool.runescape.wiki/w/Abyssal",
"https://oldschool.runescape.wiki/w/Abyssal_whip",
"https://oldschool.runescape.wiki/w/Abyssal_Sire",
...
]
]
The next step would be to open the found page in a browser tab.