I’d also mention that the tvdb API does return guest star info, since a previous comment was unsure about that. Tested against an episode and got this response:
https://www.thetvdb.com/series/community/episodes/5168505
{
"data": {
"id": 5168505,
"airedSeason": 6,
"airedSeasonID": 609588,
"airedEpisodeNumber": 9,
"episodeName": "Grifting 101",
"firstAired": "2015-05-05",
"guestStars": [
"Matt Berry",
"Ryan Ridley"
],
"directors": [
"Rob Schrab"
],
"writers": [
"Ryan Ridley"
],
"overview": "When a clever clever con man, Professor DeSalvo, uses his class to cheat the study group, they enlist Jeff to get revenge. The situation goes awry as Britta and Dean Pelton get involved in Jeff and Professor DeSalvo’s scamming competition.",
"language": {
"episodeName": "en",
"overview": "en"
},
"productionCode": "608",
"showUrl": "",
"lastUpdated": 1441749112,
"dvdDiscid": "",
"dvdSeason": 6,
"dvdEpisodeNumber": 9,
"dvdChapter": null,
"absoluteNumber": 105,
"filename": "episodes/94571/5168505.jpg",
"seriesId": 94571,
"lastUpdatedBy": 1,
"airsAfterSeason": null,
"airsBeforeSeason": null,
"airsBeforeEpisode": null,
"imdbId": "tt4242886",
"contentRating": "TV-PG",
"thumbAuthor": 1,
"thumbAdded": "2019-11-13 10:32:01",
"thumbWidth": "640",
"thumbHeight": "360",
"siteRating": 7.6,
"siteRatingCount": 405,
"isMovie": 0
}
}