Is the forest gnome's "Speak With Small Beasts" feature definitively bi-directional in 5e?

Question

Forest gnomes have the following racial feature:

Speak with Small Beasts. Through sound and gestures, you may communicate simple ideas with Small or smaller beasts.

Like many words in English, "communicate" has different senses with differing definitions. In fact, the Oxford English Dictionary (OED) has 18 different senses for the word "communicate", with a separate definition for each sense. At issue is whether the "Speak with Small Beasts" feature is using the word "communicate" in the sense of one-way communication, or two-way communication of information. The former is verb sense #1 in the OED; the latter is verb sense #8.

The OED's sense 8 is "to impart, exchange, or share information or ideas with, by means of speech, writing, signals, etc... to be in mutual communication." This means "communicate" certainly can mean mutual exchange of information.

In reading definitions, one must be aware that the preposition paired with a word makes a difference in meaning. The sense above, sense 8, is the only one in the OED that specifies the preposition "with". In other words, the phrase "communicate with" has only this sense, according to OED. So, this would seem to mean that when the RAW mentions communicating "with" small beasts, it is in the sense of a mutual exchange of information.

However, one problem. Sense 8 is listed as intransitive, meaning it should not have a direct object. But the sentence in question, in RAW, has a direct object ("simple ideas") and thus is transitive. And all the OED's verb senses that are listed as transitive, describe one-way communication, e.g. sense 1, "to convey, express; to give an impression of, put across".

Which brings us to the following point: the sentence in RAW is bad English style, because it mixes a transitive object with the preposition "with", which breaks the OED specification of this word. On the one hand, if you say "communicate (something)" and you mean it to be a one-way communication, the next preposition should be "to", not "with". Conversely, if you pair "communicate" and "with" and you also want to specify what is being communicated, then you are supposed to introduce another preposition, such as "about."

RAW does neither of these, and thus creates an ambiguity between sense 1 and sense 8 of "communicate". To make this more clear, here are two slightly modified versions of the sentence, that would have left the matter entirely clear:

"you may communicate simple ideas to Small or smaller beasts" (clearly sense 1)

"you may communicate with Small or smaller beasts about simple ideas" (clearly sense 8)

RAW did neither of those, and sort of combined the two. So semantically, it is a bit of a mess.

So, finally, the question: Is there anything else in WOTC 5e materials that clarifies whether the communication mentioned in this rule is one-way or two-way? For example, is a forest gnome NPC depicted in a published adventure as having two-way communication with a squirrel by means of this feature? Because that would settle it. Is there anything like that? Or if not, then is the answer, "It's up to the DM"?

I noticed that this answer shares rules from 3.5e that clearly indicate a two-way communication for gnomes, but I am looking for an answer within 5e materials (if there is one).

Answer 1

There are several instances in which "Communicate with" means a two-way communication.

Several spells allow the caster to communicate with other entities (animals, plants, extraplanar creatures). For example, Speak with Animals says (emphases mine):

You gain the ability to comprehend and verbally communicate with beasts for the duration. [...] beasts can give you information about [...] You might be able to persuade a beast to perform a small favor for you, at the GM's discretion.

The Speak with Plants spell allows a two-way communication:

You imbue plants within 30 feet of you with limited sentience and animation, giving them the ability to communicate with you and follow your simple commands. You can question plants about events in the spell’s area within the past day, gaining information about creatures that have passed, weather, and other circumstances.

Since you can question the plants, it likely means that they can respond.

The Planar Ally spell requires you to be able to share some common way of communication to make the bargain, hence it must be a two-way communication:

[...] You must be able to communicate with the creature to bargain for its services.

Previous uses suggest that the communication is two-way: moreover, reading the description of Forest Gnome:

These gnomes also befriend small forest animals and rely on them for information about threats that might prowl their lands.

This description, together with the above references, strongly suggests that gnomes and animals can communicate with each other.

There were other instances in which this was not the intended use.

The Great Old One warlock's Awakened Mind feature used to have the same language in a previous version:

You can communicate telepathically with any creature you can see within 30 feet of you.

But now it has been changed¹, following the Sage Advice Compendium. The new version says instead (emphasis mine):

You can telepathically speak to any creature you can see within 30 feet of you.

There is an instance² where it is stated from the beginning that the communication is one way, the following Firbolg's trait (emphases mine):

Speech of Beast and Leaf. You have the ability to communicate in a lim­ited manner with Beasts, Plants, and vegetation. They can understand the meaning of your words, though you have no special ability to understand them in return.

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¹ A change that is not listed anywhere, to the best of my knowledge: see here and here.

² Credits to biziclop that pointed this out in a comment.

Answer 2

Yes.

It says 'with beasts' not 'to beasts'.

The rest doesn't really matter.

Answer 3

Not definitely, but probably

You already highlight why the text of the feature is ambiguous in excruciating, well-researched detail. The other features that use the word "with" and are clearly bidirectional, like speak with plants, lack an object and thus are unambiguous, so looking at them does not help.

There are however several circumstantial indications that bidirectional communication is possible:

1. The Forest Gnome description (p. 37 PHB) that states they rely on small animals for information. If they only could talk to those animals to convey information, that would not work:

These gnomes also befriend small forest animals and rely on them for information about threats that might prowl their lands.

2. The name of the feature is "Speak with Small Beasts". Names are not rules text, and therefore this is not conclusive, but this could have been easily called "Speak to Small Beasts", if the intention was that you communicate only simple ideas to them, not exchange such ideas with them

There is no mention in any published material (that I am aware of) by WotC about a forest gnome having a conversaton with a small animal. The only adventures that feature forest gnomes are Wild Beyond the Witchlight and Shadow of the Dragon Queen, and neither of them has such a scene.

Because of this, the only definite answer here is "Up to the DM", but I think there is good circumstantial evidence for the DM allowing bidirectional communciation.