What can I search?

Leylines finds Magic cards by what they do. Describe it in plain English, such as creature removal under $5, and the search turns your words into tags for what a card does and filters for color, type, mana value and price. Then it lists the Commander-legal cards that match.

What it is

Describing what a card does: removal, ramp, card draw, tutors, tokens, tapping and untapping, counters, the graveyard, sacrifice, life gain, blink and more. Say whose things it acts on (“my creatures”, “opponents' creatures”) when it matters.
Filters in words: colors (“green”, “white only”, a guild name), card types (“creatures”, “equipment”), mana value (“cost 2 or less”, and “cheap” means 2 or less) and price in US dollars (“under $5”).
Doing it or rewarding it: “payoffs” and “cares about” ask for cards that benefit from something, not cards that do it.
The color picker beside the box limits a search to a color identity. It replaces any colors named in the text.
Follow-ups: after a search, press Follow up to refine what's on screen, such as same thing but white only.
Card names: names are suggested as you type, and a card's full name opens its page. A name that is also a search term, such as Flash, runs the search with a link to the card. Follow-ups don't look up names.
Deck search: on the Deck page, the search box looks for cards your deck could use, inside your commander's colors once you have one. It can also ask about the deck itself, such as what works with your commander or what to cut.
Advanced search: pick tags and filters from lists instead of typing.

What it isn't

Not Scryfall syntax. t:creature o:draw, cmc<=3 and other operators aren't supported. Say it in words, such as green creatures that cost 2 or less. For syntax searches, use Scryfall.
Not a rules-text search. Cards match by their tags, not by the words on them. When nothing you typed matches a tag, it falls back to a loose word search.
Not every idea has a tag. The tag list is fixed and small. Many keywords (such as flying) and themes have no tag yet, so those words are ignored, and the search tells you which.
Not art, flavor text, sets or printings. Nothing searches artwork, flavor text, sets, reprints or lists like the Reserved List.
Commander only. Results are cards legal in Commander. Other formats aren't searchable.
Not a chat. Text that isn't a card search, such as a homework question, isn't searched.

Good searches

Searches that work well, and why
Search	Why
cards that tap opponents' creatures	Says what the card does, and to whose creatures.
creature removal under $5	A job the card does, plus a price in US dollars.
green creatures that cost 2 or less	Colors, card types and mana value are filters, so this needs no tag at all.
landfall payoffs	“Payoffs” asks for cards that reward something, not cards that do it.
creature removal, but no wraths	“But no” leaves out cards that also do the second thing.
show me some mana rocks	Common slang works: mana rocks are artifacts that ramp.
tutors, lowest dollar price first	You can ask for an order: cheapest, lowest price, by name, most popular or best synergy.

Weak searches

Searches that only partly work, and why
Search	Why
creatures with flying	Flying has no tag yet, so only “creatures” is searched and “with flying” is ignored.
cards that make food tokens	Tags know artifact tokens, not which kind, so Treasure, Clue and Food makers all match.
ramp on the reserved list	Lists, sets and printings aren't searchable, so that part is ignored.
cards with birds in the art	Art isn't searchable, so this falls back to a word search for “birds” and “art”.
anything reprinted in a secret lair	Printings and sets aren't searchable, so this is only a loose word search.

On the Deck page

Searches for a deck, and why
Search	Why
cards that tap my creatures, in my colors	“My colors” means your commander's color identity.
After “cards that tap my creatures, in my colors”: same thing but white only	A follow-up keeps the last search and changes only what you say.

In more detail

How a search becomes tags

A new search's text goes to a language model, Anthropic's Claude, with the list of tags and filters. It answers with a structured search: tags, filters and an order. Code checks that answer, so only real tags and real card names get through. The answer is saved, so the same words in the same context give the same search.

The search can then turn out one of these ways:

All of it maps: the results show chips for each tag and filter, which you can change without a new search.
Part of it maps: the rest is listed as ignored, and the results match only what mapped.
Nothing maps: it becomes a plain word search of card names, type lines and rules text, ranked by how many of your words a card has, then by popularity (on the Deck page, by fit to your deck). These results can be loose. The same word search stands in when the language model can't be reached or its answer can't be used.
It isn't a card search: nothing is searched.
It names a card that doesn't exist: it suggests close names.
It needs a deck or commander, such as “what should I cut”: ask it on the Deck page.

Words that didn't map, and text that isn't a card search, are saved with nothing that identifies you, so the tag list can grow.

When your words have two readings, such as cards that tap creatures or cards that reward tapping them, the search picks the likelier one and offers the other as a button. If the chosen reading finds nothing, the search shows another reading that does, and says so.

Why a card matches, or doesn't

Tags come from rules that read each card's rules text, plus corrections made by hand. The language model only reads your search, never the cards. So a card shows up when its tags fit every part of the search, and its exact wording doesn't matter.

A card's page lists its tags, and each tag has a page of every card with it. If a tag looks wrong, the card's page lets you report it.
A missing card may be outside a filter. Check the chips: a color limit, a mana value, or a narrower setting such as a tap that only counts the card itself.
Card types must all be on the card, so “artifacts or enchantments” can't be written as types, and that part is ignored.
A search can have one list of alternatives (“removal or wipes”) and leave things out (“but no wraths”), but a second list of alternatives is ignored.
On the Deck page, cards outside your commander's colors never show up.

Colors and order

A color word means within those colors: “white only” includes colorless cards. “Exactly” these colors excludes the rest.
“My colors” means your commander's color identity, so it works on the Deck page with a commander, not on the home search.
You can ask for an order: cheapest first, lowest price first, by name, most popular, or best synergy.