Coins are data

Which items are money, and what they're worth, is the medici:coin_values data map: data/medici/data_maps/item/coin_values.json in your datapack (a data map's files always sit in the map's own namespace, medici, whatever namespace your pack uses; NeoForge merges the files of every pack). Medici's own:

{
  "values": {
    "medici:penny": { "value": 1, "symbol": "P" },
    "medici:groat": { "value": 10, "symbol": "G" },
    "medici:ducat": { "value": 100, "symbol": "D" }
  }
}

Add a coin (any item, any value in pennies, a short symbol for prices) or change values in a datapack. Every Medici block reads this map; change-making works with any set (a 25-penny coin is fine). Tags: #medici:coins, #c:coins, #medici:coins/copper|silver|gold.

Turning sources down

All new money passes the decree (medici-server.toml, CONFIG). Fewer coins on your server: lower targetPerPlayer. No mob coins: mobCoinsPerDay = 0.

Found money

• Mob drops: data/<ns>/medici/mob_drops/*.json, first matching rule wins; files are read in order of their path, then their namespace (a.json before b.json, whatever the namespace): {"entities": ["minecraft:pillager", "#c:bosses"], "chance": 0.6, "min": 1, "max": 3, "rare_value": 10, "rare_chance": 0.08, "antiques": 0, "antique_chance": 0} (pennies). Only real player kills of mobs that spawned naturally, from world generation, structures, patrols or raids pay; spawners, eggs, breeding and machines never do. Daily cap per player: mobCoinsPerDay.
• Chest loot: the global loot modifier medici:coins_in_chests (data/medici/loot_modifiers/coins_in_chests.json) holds rules {"tables": ["minecraft:chests/village/*", "yourmod:*"], "chance", "min", "max", "antiques", "antique_chance", "letter_chance"}. Override the file in a datapack to add your structures.
• Antique coins: the medici:antique_values data map (item → pennies paid at a bank counter), in data/medici/data_maps/item/antique_values.json.
• Appraisal: data/<ns>/medici/appraisal/*.json, {"values": {"minecraft:bread": 0.5, "#c:ingots/iron": 0.6}} (pennies per item; files in order of their path, then namespace, later entries override earlier ones). The Merchant wishes for items priced 0.01 to 40 p: every item listed by id, plus every item in the medici:merchant_wishes item tag that the appraisal prices at all (by id or through a tag entry). Tagged items come up 4 times as often. Add your mod's legal goods to both: a price here, an entry in data/medici/tags/item/merchant_wishes.json.

KubeJS

With KubeJS (2101.7+, as in ATM10 8.4) Medici adds three things to server scripts. Examples you can copy are in examples/kubejs; CI loads every one of them on a test server.

Events: MediciEvents.<name>(event => …). They fire before anything moves; event.cancel() refuses the action (the player sees "Not allowed here") and nothing changes.

Event strings are Java strings: compare with String(event.kind) === 'sale'.

MediciDecree: supply(server) (coins in the world, pennies), houseLeft(player) (what their house may still mint today), wallet(player) (coins they carry), format(pennies) (1D 4G 5P), and charge(player, pennies, reason): takes the coins (purses first, change given) and burns them through the mint ledger; false if they can't pay. Scripts can burn but never mint: new coins only come from the decree.

Recipe schema: event.recipes.medici.minting(result, metal, die) with optional .energy(fe) and .time(ticks).

Other mods can use the same events in Java: de.benkl.medici.api.MediciEvent.* on NeoForge.EVENT_BUS.

More (KubeJS events, recipe schemas) as the features land (#52).

Java API: MediciTreasury

For mods that pay or charge players money (traders, contracts, quest boards): de.benkl.medici.api.MediciTreasury. It keeps Medici's rule that new coins only come from the decree (ECONOMY §2): your mod registers a purse, a Medici bank account (trader:<purse id>) that takes in the coins your traders earn and pays out from them first, then from the decree's street share. Registering a purse turns that share on; a server without your mod keeps the old split.

Compile against the API jar from the release (medici-<version>-api.jar, only de.benkl.medici.api, with sources) and guard every call with ModList.get().isLoaded("medici"):

dependencies { compileOnly files("libs/medici-1.21.1-1.1.0-api.jar") }

// during setup (any thread)
MediciTreasury.registerPurse("mymod:street");

// on the server thread
long paid = MediciTreasury.pay(player, "mymod:street", 250, "mymod:contract");   // 0..250, purse first, then the street
if (MediciTreasury.charge(player, "mymod:street", 40, "mymod:shop")) { /* hand over the goods */ }
Component price = Component.literal(MediciTreasury.format(40));                   // "4G"

Amounts are pennies. Everything but registerPurse/isRegistered runs on the server thread only. A purse id that isn't registered makes withdraw, deposit, pay and charge throw IllegalArgumentException. At each decree day start a purse keeps at most max(1,000 p, 3 × the street pool); the rest is burned, so pay out what you take in.

Add your own art

Everything the Artist paints is data (concept §4.9.3), read on /reload; a bad file is logged and skipped. Ids are <namespace>:<path>; names come from lang keys art.<ns>.<path with dots> (motifs), frame.<ns>.<id>, pose.<ns>.<id>, theme.<ns>.<id>.

• Motifs data/<ns>/medici/art/motif/**/*.json:

  { "kind": "portrait", "theme": "medici:canal", "rarity": "uncommon", "set": "my_pack",
    "texture": "mypack:art/background/harbour", "masterwork_texture": "mypack:art/background/harbour_night" }
  

  kind: portrait (textures textures/<texture>_<w>x<h>.png for 1x1, 1x2, 2x2, 3x2 at 16 px per block), city_view ("painting": "mypack:harbour" = a painting_variant you also add, with "sizes": ["3x2"]; "dimension" hides it until that dimension exists), fresco (textures/<texture>_<w>x<h>.png on the block atlas, i.e. under textures/block/, sizes 2x2, 3x3, 4x3, 6x4), mask (texture namespace + pattern id: textures/models/armor/mask/<shape>_<pattern>.png and item/mask/<shape>_<pattern>.png), crest ("pattern": a banner_pattern), statue ("ramp": ["#rrggbb", …] dark → light), colossus ("scheme": {"shades": […], "core", "ornament", "eyes", "plinth", "plinth_trim"}, block ids). rarity (common 6 : uncommon 3 : rare 1 weight) decides the odds: Sketch draws common, Study common and uncommon, Commission and up everything. Optional "sizes" limits a motif to some sizes.
• Frames data/<ns>/medici/art/frame/*.json: {"family": "wood", "texture": "mypack:art/frame/oak", "shape": "rect"}; the texture is a 16×16 nine-slice with a 3 px border; families plain (Sketch), wood (Study), gilt (Grand, or Commission with gold leaf), anything else from Commission tier; shapes rect, oval, round.
• Poses data/<ns>/medici/art/pose/*.json: {"kinds": ["portrait", "statue"], "bust_only": false}; the built-in drawing knows standing, hand_on_hip, holding_ducat, ledger_and_quill, gondolier_oar, masked, pointing, seated, orator, saluting (other ids draw as standing).
• Themes data/<ns>/medici/art/theme/*.json: {"order": 20}.

Missing textures show a plain canvas (portraits) or the missing-texture sprite (frescos), never a crash. To change prices or pools in code, listen to de.benkl.medici.arts.CommissionEvent (see INTEGRATIONS).