Who decides which check to make on a recall knowledge action?

Question

In Pathfinder 2, a character can attempt a Recall Knowledge check to get some information about a monster. There are several skills that can be used for such checks, but only some of them work for any given monster.

Let's assume a player decides to use Recall Knowledge on an animated armor (as a Construct it can be identified with either Arcana or Crafting). How does it work? Here are two guesses:

• The player chooses one skill she wants to use (either Arcana, Crafting, or maybe Religion if she thinks it might be an armor possessed by a ghost). The player rolls and the DM tells her information she learns associated to that specific skill (for example if the player chose the skill Nature and rolled well the DM would say "this is definitely not an animal, a plant, a fey, or some other natural thing")
• The DM tells the player about which skill to roll (depending on what the monster is and which skills the character is trained in). The player rolls this skill and eventually gets more information.

The first hypothesis seems more natural to me as a DM but my players told me it wasn't supposed to work like that. Who is right?

Answer 1

Generally, the player decides

From the Recall Knowledge entry in Skills and Action,

The following skills can be used to Recall Knowledge, getting information about the listed topics. In some cases, you can get the GM’s permission to use a different but related skill, usually against a higher DC than normal. [...] The GM might allow checks to Recall Knowledge using other skills. For example, you might assess the skill of an acrobat using Acrobatics.

As written, the player declares that they are trying to Recall Knowledge using (Skill). The GM then decides if that is an acceptable action and rolls the check (it's a Secret check), providing any information (or lack thereof) gained.

However, it's not unreasonable to ask which skill(s) would be appropriate

The list of "appropriate" skills are a generic list that allow you to get going. There are instances where a GM may wish to deviate from the provided table; for example, it would not be unreasonable to allow Recalling Knowledge about a Flesh Golem using Religion to compare it to undead (in addition to Arcana and Crafting). I'm sure there are creatures that normally appropriate skills don't make sense. There is no reason the GM couldn't let the players know which skills they intuit would be effective.

Of course it is up to each group if this is something that is allowed, regular, or if the players expect the GM to be upfront about the skill examples provided. As written, the GM is under no obligation to provide anything more than a description of the creatures encountered.

In my experience, it goes most smoothly when the GM is upfront about what skill(s) are acceptable to roll unless there's a reason the characters wouldn't know to roll that skill (IE illusion magic). Trying to limit player knowledge more than character knowledge rarely pans out well; it does not magically remove meta play nor does it provide fun moments.

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Side note: Failing Forward

When the player spends an action, they're usually hoping to get some benefit. For 1/3 of their turn, it's not unreasonable to make a best effort to provide some information, even if it's less useful than they hoped.

Following off your example, you may tell the player rolling Nature "This being seems wholly un-natural... constructed and magically empowered." to inform them of more appropriate skills. If they were instead attempting to roll Religion (and rolled sufficiently high, probably against a greater-than-normal DC), you may be able to provide some details about the creature "You realize it's not actually possessed... it would respond to positive energy if so, but this thing doesn't and seems to be resisting physical damage, like an object".