My player wants to take this homebrew cantrip he found.

[Corinath]

https://www.dandwiki.com/wiki/Detect_Secrets_(5e_Spell)

So, for background, he's built his entire character identity around being an investigator. His background was basically similar to the FBI for a particular kingdom, and he accrued those skills because he's spent the last five years searching for his missing brother. Their adoptive father was also a great detective.

If it matters, he's a Celestial Warlock who just became a Pact of Tome, so he was looking for new cantrips to add,

In terms of balance, no one is "competing" with him for the identity of being a detective, with exception of a Blood Hunter who only uses those skills to route out Blood Hunter-y things.

I'm inclined to give it to him, because you can already get advantage with the "help" action anyway, and because of the above.

How would you rule? Would you decline it? If so, why?

[Teaguethebean]

I see it as kinda weak considering taking Guidance is just that but a little weaker and considerably more versatile. I would recommend to him Guidance as an alternative as I don't really like throwing in homebrew.

[Corinath]

Yeah that's one thing I was considering.

One way that "strengthens" it, is that I only allow two D20 rolls for party activities, such as group investigating, otherwise my party of 6-7 would roll 6-7 D20s and at least one of them would roll high enough in general.

But what I like about Guidance is a way I could flavor it for his character in particular, and that he could use it on other people. We have no clerics or druids that would otherwise take that cantrip.

[Vogie]

It effectively makes them not have to invest in Wisdom or Intelligence at all. I'd probably limit it to 1 minute (like Friends) rather than a 10 minute duration

However, as long as you require them to apply it before you call for a perception check, it'd be okay. That is, they have to turn it on actively when they know they're going to go exploring - it can't be a "Roll Perception" "I cast detect secrets for advantage!" unless you reply with "Okay, as you start casting a spell, you are struck by an arrow and spend the first round surprised"

[Corinath]

It effectively makes them not have to invest in Wisdom or Intelligence at all. I'd probably limit it to 1 minute (like Friends) rather than a 10 minute duration

However, as long as you require them to apply it before you call for a perception check, it'd be okay. That is, they have to turn it on actively when they know they're going to go exploring - it can't be a "Roll Perception" "I cast detect secrets for advantage!" unless you reply with "Okay, as you start casting a spell, you are struck by an arrow and spend the first round surprised"

LoL yeah I wouldn't let them use it like that.

Friends is another good cantrip to use as a comparison. That's a good idea. Since he's a Warlock, INT and WIS aren't his strongest suits, but per his backstory it's something he likes using a lot.

[Sigreid]

I would limit it to one check that he was intentionally making. Beyond that, he'd still have to invest in Int and Wis because Advantage is great but it absolutely does not let you hit higher numbers than you could otherwise manage.

[Dalebert]

Characters just help each other on those things and have adv anyway. Seems weak

[Corinath]

Characters just help each other on those things and have adv anyway. Seems weak

Per above, I only allow 2D20s on group activity checks, like investigating a room, otherwise we're rolling with advantage 7 times to uncover a hidden item.

This would allow one player to have advantage by default, and allow a second player to roll normally, upping the group investigation check to 3d20s.

However, that being said, yeah, it does seem weak in some ways, particularly since spells like guidance fall on top of advantage.

[Arcangel4774]

Your 2d20 only rule seems rational enough, but an arbitrary cut off. The help action has one person giving onother person advantage. This cantrip is similarly one person giving himself advantage. Cutting the number of checks makes some sense. Limiting advantage, while a bit wierder is fine when consistant, i guess. But allowing advantage to this case only seems a bit like arbitrary favoritism.

[ProsecutorGodot]

Keep in mind that having advantage also increases his passive perception/investigation. Whether you want that to be something so readily available depends on how many hidden enemies/traps you plan on having.

By itself, it's fairly tame though.

EDIT: My DM would tell you that it created issues with things like secret doors and ambush encounters. My Inquisitive Rogue had a passive investigation/perception score of 27 which made him more perceptive than an Ancient Red Dragon. He's retired, but leveling him behind the scenes for fun has his passive scores over 30.

This cantrip would have allowed him to have that score over 30 prior to his retirement at level 8.

[Lunali]

Per above, I only allow 2D20s on group activity checks, like investigating a room, otherwise we're rolling with advantage 7 times to uncover a hidden item.

Even under normal rules you can't both help and search. If you're meaning it would allow them to help then search or search then help, that would also mean they can search then search, meaning they can just keep attempting until they're confident they've found everything they can.

If you're going to have investigation as a significant part of your campaign, you should either have time constraints or let them effectively take 20 on their searches.

[crayzz]

I see it as kinda weak considering taking Guidance is just that but a little weaker and considerably more versatile. I would recommend to him Guidance as an alternative as I don't really like throwing in homebrew.

Specifically, the average roll with Advantage is just under 14, whereas with guidance the average roll is 13.

I'd probably just make is a more targeted version of guidance, giving 1d4+1 to perception and insight checks, and make it only last a minute.

[Kane0]

Might I propose an alternative:

Detect Secrets
Divination cantrip
Casting time: 1 action
Range: Self
Components: V
Duration: Concentration, up to 10 minutes

For the duration of the spell, whenever you make an intelligence or wisdom ability check that lets you add your proficiency bonus, you can treat a d20 roll of 4 or lower as a 5.
Optionally, scale it up at the usual cantrip levels to make the minimum roll 6, 7 and 8.

Works better with Guidance, advantage and expertise. Also potentially applies to other skills if you happen to be proficient. Might want to adjust the name but no big deal.

[BloodSnake'sCha]

I will warn the player that it is a weak cantrip and let them take it.
There are common items that to that and the help action.

[Mercurias]

I feel it were me, I’d steer the player towards the Guidance cantrip instead and recommend they ask a friend to assist them with a search.

My big worry with this cantrip is that it’s an excuse for your player to get possessive over a particular aspect of the game. Whenever possible, I usually encourage players to interact.