How does Wall of Force grant cover?

Question

Which mechanic of wall of force gives cover to creatures on either side of the wall?

It grants attributes similar to cover. It specifically states cover-like effects against physical and astral projections, but does not explicitly grant cover in its description. This leads me to believe it does not grant cover or a cover-like status in all situations.

This is not a duplicate question as other wall of force questions assume that the wall grants cover as their answer, but I don't feel they properly explain how that conclusion is reached.

This question is not how does wall of force prevent gaze attacks or magic attacks. It is targeted at the popular assumption that wall of force grants cover. I do not understand it, so I need help with this clarification.

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Premise:

1. "Spells only do what they say they can do."
2. In the spell description, it does not grant the "cover" attribute to creatures on either side of the wall. Cover is not mentioned anywhere in the spell description.
3. "[The wall] is immune to all damage and can’t be dispelled by dispel magic. A disintegrate spell destroys the wall instantly, however."
4. As per 3, the wall is not immune to magic, nor does it say it has anti-magic properties similar to the antimagic field spell.
5. "Nothing can physically pass through the wall." Grants an effect similar to cover, but does not apply the cover attribute.
6. The spell explicitly states that physical and astral projections cannot pass through the wall. By exclusion, anything else can.
7. It does not block line of sight. The wall is invisible.
8. Does not state the wall is tangible.
9. Does state the wall is made of force
10. "Force" is a damage type. Damage types are attributes, not substances. Cold, Fire, ice, Necrotic etc. as a damage type - in and of themselves are not physical or tangible forces.
11. There are no examples of a damage type granting cover.
12. Magic is not a physical effect and is not subject to the "Nothing can physically pass through the wall." descriptor.

I have tried to ask isolating questions to try and narrow down a few of the issues I have with the popular ruling:

• The Invisible Barrier granting cover paradox. (On hold)
• Damage Types Granting Cover
• Is Magic Physical, Astral, or Other?

So my question stands: How does wall of force grant cover to characters on either side of the wall?

It grants attributes similar to cover. It specifically states cover like effects against physical and astral projections, but does not explicitly grant cover in its description. This could lead one to believe it does not grant cover in all situations.

Answer 1

A wall of force grants cover by being an obstacle. A confirmed tweet from a game designer states this includes spells.

According to the cover rules in the Player's Handbook, p.196:

Walls, trees, creatures, and other obstacles can provide cover during combat, making a target more difficult to harm. [...] A target has half cover if an obstacle blocks at least half of its body [...] A target has has three-quarters cover if about three quarters of it is covered by an obstacle [...] A target has total cover if it is completely concealed by an obstacle.

Is a wall of force an obstacle? In D&D 5th edition, words not defined in game rules are interpreted according to their standard English meaning.

Something that impedes, stands in the way of, or holds up progress.

The description of the wall of force states:

Nothing can physically pass through the wall.

Therefore, the wall of force is an obstacle, and being behind it relative to your opponent grants you cover.

If I understand your recent questions correctly, you hope to learn whether wall of force specifically blocks magic, on the hypothesis that magic is not "physical". The rule on casting spells against people behind obstacles appears in the Player's Handbook, page 204:

To target something, you must have a clear path to it, so it can't be behind total cover.

D&D 5e designer Jeremy Crawford, whose rulings are considered official, confirms in a tweet that wall of force provides total cover:

Q: could a wizard make a sphere around a creature using wall of force and then chill touch to damage them through the wall?

Crawford: Unless a spell says otherwise, you can't target someone behind total cover (PH, 204)

Also here, in specific reference to wall of force:

Cover is a physical obstruction, not necessarily a visual one.

While the cover rules say that total cover "completely concealed", a term which in earlier editions of D&D referred specifically to visibility and not cover, Crawford here appears to clarify that "concealed" is a synonym here for "covered". Note how the other two forms of cover say "blocks" and "covered", so it seems that they're using synonyms to avoid repetition.

Therefore, regardless of the "physicality" of magic, the official ruling on this issue is that wall of force provides total cover, and therefore blocks magic.

Answer 2

It's in the way it works.

I'm pulling heavily (well, entirely) from SevenSidedDie's answer here.

Nothing being able to pass through the wall makes it count as total cover, and that makes targets on the other side of it invalid spell targets. From "Targets" in the PHB's Spellcasting chapter, page 204:

To target something, you must have a clear path to it, so it can't be behind total cover.

Greenstone Walker's comment here is also relevant to understanding the issue of concealment vs cover:

It is possible to have total cover but no concealment. For example, being in the middle of a gelatinous cube.