§05 · API

Launch API

Build a launch with the site's rules, sign it, send it privately, track it.

The flow

Build. POST /v1/launches with the creator wallet and the coin fields. The server runs the same checks as the site, picks the config for the fee option, adds the dev buy and the Jito tip, simulates, and returns a base64 v0 transaction plus signers.
Sign. The creator wallet signs (and your mint key, if you sent a custom mint). Signers can sign in any order.
Submit. POST /v1/launches/{id}/submit within about 60 seconds. It is sent through Jito, privately, and answers live or submitted within waitMs (default 20 s).
Track. Poll GET /v1/launches/{id}, or listen for launch.created on a webhook or the launches channel.

SDK: all four steps

const r = await justi.launch({ signer: wallet, name: "Swordope", ticker: "SWORD", image, mode: "split", creatorBps: 50 });
// r.status: "live" | "submitted" | "failed" | "expired"; r.mint, r.signature, r.url

Fields and rules

Field	Rule
wallet	Creator wallet. Pays, signs, becomes the pool creator and earns the creator fee.
name	2 to 32 characters.
ticker	2 to 10 letters or numbers. A leading $ is dropped.
image	https URL (fetched by the server: public hosts, 5 MB, 8 s) or a data URL up to 500 KB. Large images are re-encoded to WebP.
banner	Optional 3:1 banner shown on the site. Not on chain.
mode, creatorBps	creator: 0 to 250 in steps of 25. holders: 0. split: 25 to 200 (plus 0.5% to holders).
devBuyLamports	Optional. Capped at 15% of supply; the cap per option is in GET /v1/pad (maxDevBuyLamports, about 4.665523 SOL on the lowest fee option).
xUrl, telegramUrl, website	Optional links, stored in the metadata.
mint	Optional custom mint public key. See below.

Refusals have clear codes: copy_exists (409, with details.existing), launch_limit (429, 10 per wallet a day), image_fetch_failed, mint_taken, insufficient_funds. See Errors.

Custom (vanity) mints

Without mint, the server uses a key ending in JUST from its pool and signs that slot before returning. To use your own vanity mint, grind the keypair yourself, send only its public key as mint, and sign the returned transaction with it. The API has no field for a secret key and never needs one.

const mintKp = Keypair.fromSecretKey(myGroundKey); // stays on your machine
const r = await justi.launch({ signer: wallet, mintSigner: mintKp, name: "Bunnett", ticker: "BUNNETT", image, mode: "holders" });

Note

signers[] in the build response lists every slot: payer and mint, with signed: true when the server already signed it.

Reference

#Build a launch exactly like the site does

POST/v1/launches

Key optionalRate class launchBody 3mbbuildLaunch

Same validation as the site: copy rule, 15% dev-buy cap, tier configs, sniper window, 10 launches per wallet a day. Returns an unsigned (by the wallet) v0 create transaction. signers lists every required signature: the payer (wallet) always; the mint is already signed for pool keys, or must be signed by your client with your custom mint keypair. Then POST /v1/launches/{id}/submit with the fully signed transaction within about a minute.

Body

Field	Type	About
walletrequired	address	Creator wallet: pays, signs, is the pool creator.
namerequired	string	max 32 chars
tickerrequired	string	2 to 10 letters or numbers; a leading $ is dropped. max 11 chars
description	string	max 280 chars, default ""
imagerequired	string	https URL (fetched by the server: public hosts only, 5 MB max, 8 s) or a data:image/...;base64 URL up to 500 KB. max 700000 chars
banner	string \| null	Optional 3:1 banner, https URL or data URL (1 MB). Site only, not on chain. max 1400000 chars
xUrl	string \| null	max 200 chars
telegramUrl	string \| null	max 200 chars
website	string \| null	max 200 chars
moderequired	"creator" \| "holders" \| "split"	Who earns the fee: the creator, holders, or both.
creatorBps	integer	Creator fee in bps (creator: 0-250 step 25; split: 25-200 step 25; holders: 0). default 0
devBuyLamports	u64 string	Dev buy in the create transaction. Capped at 15% of supply. default "0"
mint	address	Custom (vanity) mint public key. The integrator's client holds the keypair and signs the returned transaction with it. Never send the secret key. Without it the server uses a ...JUST key from its pool (already signed in).
hidden	boolean	Admin only (X-Admin-Token header): the coin never appears on the board, live feeds, token list or stats. Its page and APIs by mint still work.
testConfig	boolean	Admin only (X-Admin-Token header): launch on the server's test config (holders tier, low graduation threshold). Always hidden.

Response LaunchBuilt

Field	Type	About
launchIdrequired	string	UUID.
mintrequired	address
customMintrequired	boolean
vanityrequired	boolean	A ...JUST key from the pool.
signersrequired	object[]
pubkeyrequired	address
rolerequired	"payer" \| "mint" \| "other"
signedrequired	boolean
curvePoolrequired	address
configrequired	address
tierrequired	string
feesrequired	object
tierrequired	string
moderequired	"creator" \| "holders" \| "split"	Who earns the fee: the creator, holders, or both.
totalPctrequired	number
platformPctrequired	number
creatorPctrequired	number
holdersPctrequired	number
protocolPctrequired	number
creatorOnchainPercentrequired	number
poolFeeNumeratorrequired	u64 string	Unsigned integer as a decimal string (may exceed 2^53).
devBuyLamportsrequired	u64 string	Unsigned integer as a decimal string (may exceed 2^53).
devBuyTokensrequired	u64 string	Unsigned integer as a decimal string (may exceed 2^53).
devBuyPctOfSupplyrequired	number
bytesrequired	integer
computeUnitsrequired	integer \| null
tipLamportsrequired	u64 string	Unsigned integer as a decimal string (may exceed 2^53).
lastValidBlockHeightrequired	integer
metadataUrirequired	string
imagerequired	string
transactionrequired	string
hidden	boolean	Present when the launch was built hidden (admin).
testConfig	boolean	Present when built on the test config (admin).

Errors400 bad_request, insufficient_funds, chain_rejected, image_fetch_failed, invalid_params, invalid_json401 unauthorized403 forbidden409 copy_exists, mint_taken413 payload_too_large429 launch_limit, rate_limited500 internal503 unavailable

curl -X POST "https://api.justi.fun/v1/launches" \
  -H "Content-Type: application/json" \
  -d '{"wallet":"<wallet>","name":"Kurumi","ticker":"KURUMI","description":"hold the line.","image":"https://example.com/kurumi.png","mode":"holders","creatorBps":0,"devBuyLamports":"100000000","mint":"<mint>"}'

#Send a signed launch (Jito, private)

POST/v1/launches/{id}/submit

Key optionalRate class submitBody 16kbsubmitLaunch

The transaction must be exactly the built message with every required signature. Answers live, or submitted after waitMs (default 20000); poll GET /v1/launches/{id}.

Parameters

Name	Type	About
idrequiredpath	string	UUID.

Body

Field	Type	About
transactionrequired	string	Base64 serialized versioned transaction. max 4000 chars
waitMs	integer	0 to 60000

Response LaunchSubmitted

Field	Type	About
statusrequired	"live" \| "submitted"
mintrequired	address
signaturerequired	string

Errors400 tx_mismatch, signature_invalid, chain_rejected, bad_request, invalid_params, invalid_json401 unauthorized404 not_found409 already_submitted410 expired413 payload_too_large429 rate_limited500 internal

curl -X POST "https://api.justi.fun/v1/launches/<id>/submit" \
  -H "Content-Type: application/json" \
  -d '{"transaction":"<signed base64 transaction>"}'

#Launch status

GET/v1/launches/{id}

Key optionalRate class readgetLaunch

Parameters

Name	Type	About
idrequiredpath	string	UUID.

Response Launch

Field	Type	About
launchIdrequired	string	UUID.
statusrequired	"built" \| "submitted" \| "live" \| "failed" \| "expired"
mintrequired	address
curvePoolrequired	address
configrequired	address
tierrequired	string
creatorrequired	address
namerequired	string
tickerrequired	string
customMintrequired	boolean
signaturerequired	string \| null
errorrequired	string \| null
devBuyLamportsrequired	u64 string	Unsigned integer as a decimal string (may exceed 2^53).
devBuyTokensrequired	u64 string	Unsigned integer as a decimal string (may exceed 2^53).
lastValidBlockHeightrequired	integer
metadataUrirequired	string
imagerequired	string
viaApirequired	boolean
partnerrequired	string \| null	Label of the API key that built it.
createdAtrequired	integer	Unix time in seconds.
updatedAtrequired	integer	Unix time in seconds.

Errors400 invalid_params401 unauthorized404 not_found429 rate_limited500 internal

curl "https://api.justi.fun/v1/launches/<id>"

#The flow

#Fields and rules

#Custom (vanity) mints

#Reference

#Build a launch exactly like the site does

Body

#Send a signed launch (Jito, private)

Parameters

Body

#Launch status

Parameters

The flow

Fields and rules

Custom (vanity) mints

Reference