> For the complete documentation index, see [llms.txt](https://docs.nexus.xyz/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.nexus.xyz/api-reference/account/fetch-deposit-address.md).
# GET /account/deposit-target
How to fund this account
How to fund this account.
`operationId`: `fetchDepositAddress` · CCXT method: `fetchDepositAddress`
> **Declared server:** `https://api.testnet.nexus.xyz/v1`. See [Networks](/api-reference/guides/networks.md).
**Authentication:** `agentAuth`, `hmacAuth`.
## How to fund this account
> Machine-readable funding instructions for the authenticated account, so an autonomous client can fund itself without out-of-band knowledge of how a given deployment accepts collateral.\
> \
> \*\*The response is a discriminated union on \`mode\`, and which mode you get is a property of the deployment, not of the request.\*\* Branch on \`mode\`; do not assume either shape. A deployment with a real deposit-contract address configured answers \`onchain\`; otherwise it answers \`testnet-faucet\` and points at its synthetic-credit endpoints. There is no request parameter that selects between them.\
> \
> An address is never fabricated to fill the \`onchain\` shape. A deployment configured for on-chain deposits whose address is malformed refuses with \`503\` rather than silently falling back to the faucet, because depositing to a bad address burns the funds.\
> \
> \`confirm\` is identical in both modes and is the portable primitive: poll \`GET /account\` until \`balance\` reflects the funds.\
> \
> This operation is \*\*discovery only\*\*. It moves no funds, creates no deposit, and has no side effect — acting on the returned \`faucet\` or \`onchain\` instruction is a separate, explicit step by the caller.
````json
{"openapi":"3.1.0","info":{"title":"Nexus Exchange API","version":"0.9.101"},"tags":[{"name":"Account","description":"Balance and order management"}],"servers":[{"url":"https://api.testnet.nexus.xyz/v1","description":"Public testnet (play funds) — the default server and /v1 transport base for unversioned paths."},{"url":"https://api.nexus.xyz/v1","description":"Mainnet — **REAL FUNDS**. Collateral is USDX bridged from Ethereum Mainnet; orders placed here move real money, and there is no faucet. The durable per-network base. Listed after testnet on purpose, so nothing that reaches for \"the first https server\" lands on the real-funds target. Not resolvable yet: DNS/TLS is a separate infra change."},{"url":"http://localhost:9090","description":"Local development — the indexer served directly. Not a public network; whatever your local instance holds."}],"security":[{"hmacAuth":[]},{"agentAuth":[]}],"components":{"securitySchemes":{"hmacAuth":{"type":"apiKey","in":"header","name":"X-API-Key","description":"HMAC API key authentication. Send three headers:\n- `X-API-Key`: your key ID (e.g. `nx_a1b2c3...`)\n- `X-Timestamp`: current time in unix milliseconds\n- `X-Signature`: `hex(hmac_sha256(secret, timestamp + \"\\n\" + METHOD + \"\\n\" + path + \"\\n\" + query + \"\\n\" + sha256_hex(body)))`\n\nTimestamp must be within 30 seconds of server time.\n\n**The key is network-scoped; the signature is not.** The canonical string above has no network component, so the same signed request is byte-identical on every host. What stops a testnet key from authenticating against mainnet is that the key does not exist in that host's key store — sign only for the host that minted the key, and never replay a signed payload against another network. Presented to the wrong host, a key is refused with the same opaque `401` as an unknown key and must not be retried there. See “API keys are bound to one network” in the API description."},"agentAuth":{"type":"apiKey","in":"header","name":"x-agent","description":"Agent-key request signing. An agent is a secp256k1 keypair the wallet delegates trading to with `POST /agents/register`; the agent then signs each request itself, so the wallet key is never exposed. Send four headers:\n\n- `x-agent`: the agent's 20-byte address, hex, `0x` prefix optional — derived from its public key exactly like a wallet address (`keccak256(uncompressed_pubkey[1..])[12..]`). It must be registered on this host and not expired.\n- `x-timestamp`: the current time in unix milliseconds, as a base-10 integer.\n- `x-nonce`: an unsigned 64-bit integer, base 10. Required on every request; see “Nonces” for when it is enforced.\n- `x-signature`: `0x` followed by the hex of the 65-byte signature described under “Signature”.\n\n**Canonical string.** Six fields joined by LF (`\\n`), with no trailing newline:\n\n```\n{METHOD}\\n{path}\\n{query}\\n{sha256_hex(body)}\\n{x-timestamp}\\n{x-nonce}\n```\n\n- `METHOD` is upper-cased. The field order differs from `hmacAuth`: the method comes first and the timestamp comes after the body hash, so an HMAC canonical-string builder cannot be reused.\n- `path` is the logical path the server authenticates, with no host and no query string — the same rule as `hmacAuth`; see “Base paths and the signed path” in the API description.\n- `query` is the raw query string exactly as sent, without the leading `?`. With no query it is the empty string, and its line stays in the string as an empty line; it is never dropped.\n- `sha256_hex(body)` is the lower-case hex SHA-256 of the exact body bytes sent. A request with no body hashes the empty byte string (`e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855`).\n- `x-timestamp` and `x-nonce` are the same decimal strings sent in those headers.\n\n**Digest.** `keccak256(utf8(canonical_string))`: raw Keccak-256 of the canonical string, **with no EIP-191 prefix and no EIP-712 structure**. A wallet library's `signMessage` / `personal_sign` adds the `\\x19Ethereum Signed Message:\\n` prefix, which produces a different digest and a signature that recovers to some other address. Sign the 32-byte hash directly (for example `eth_account`'s `unsafe_sign_hash`, or `@noble/curves` `secp256k1.sign(digest, key)`).\n\n**Signature.** Recoverable secp256k1 ECDSA over the digest, sent as 65 bytes `r (32) ‖ s (32) ‖ v (1)` with `v ∈ {27, 28}`. `s` must be low (at most half the curve order, per EIP-2). A high-S signature is refused even though it recovers the same signer, because accepting it would let one authorization be presented as two. The server recovers the signer from the digest and requires it to equal `x-agent`.\n\n**Freshness.** `x-timestamp` must be within ±30 seconds of the server's clock, on reads and writes alike. That window is the only bound on how long a captured read signature can be replayed.\n\n**Nonces.** The nonce is parsed on every request but enforced only on writes:\n\n- On a mutating method (anything but `GET`, `HEAD`, `OPTIONS` and `TRACE`), `x-nonce` must be strictly greater than the highest nonce this host has already accepted on a write from the same agent. The accepted value is persisted before the response is sent. Each agent address has its own nonce space, separate from the wallet-signed nonces of `POST /agents/register` and `POST /withdrawals`.\n- On a read, the nonce is neither checked nor consumed, so the same signed read verifies more than once inside its ±30 s window.\n\nA counter of `max(last + 1, now_ms)` is a simple nonce source: it is unique per signer and stays increasing across restarts.\n\n**Concurrent writes from one agent can be refused as replays.** The rule is about arrival order, not issue order. When two writes from the same agent are in flight together and the one with the higher nonce arrives first, the other is refused, and the refusal is the same opaque `401` as a bad signature. The fix is still being decided (ENG-17010). Until then, keep one write in flight per agent key, or register a separate agent key for each concurrent writer.\n\n**Failures are opaque.** Any failure returns the same `401` body with no reason (see the `Unauthorized` response): an unknown or expired agent, a stale timestamp, a malformed header, a wrong digest, a high-S signature or a replayed nonce all look alike. This contract does not say which check failed or in what order the checks run, and a client must not infer either. If a signer is rejected, check it against the test vector below before anything else.\n\n**What an agent key cannot do.** Agent keys are trade-only. **An agent key cannot withdraw**, and it cannot move funds off the account by any route:\n\n- `POST /api/v1/bridge/withdrawals` refuses an agent-signed request with `403` (code `AGENT_CANNOT_WITHDRAW`). The engine's withdrawal route is refused the same way.\n- `POST /withdrawals` requires the wallet's own EIP-712 signature in the body, which an agent key cannot produce.\n- The ordinary-transfer operations (`ownerSignature`) refuse any request that carries `x-agent`.\n\nAgent keys also cannot manage agent credentials: `GET /agents`, `PATCH /agents/{address}` and `DELETE /agents/{address}` refuse them with `403` (code `AGENT_KEY_FORBIDDEN`). A client that holds only an agent key manages them with the wallet's own signature instead (`walletSignature`). And they cannot mint the legacy `POST /ws-tokens` token, which is HMAC-only; use `POST /ws/token`. None of these operations lists `agentAuth`. Every operation that does list it accepts it.\n\n**Test vector.** The key below is a public test key: never fund it or register it. The `x-nexus-test-vectors` extension on this scheme carries this vector and two more (an empty-body `GET`, and a `DELETE` with a query). Together they cover both values of `v`.\n\n- private key: `0x4c0883a69102937d6231471b5dbb6204fe5129617082792ae468d01a3f362318` → `x-agent: 0x2c7536e3605d9c16a7a3d7b1898e529396a65c23`\n- request: `post /orders` (the method is lower-case on purpose; the canonical string upper-cases it), no query, body `{\"market_id\":\"BTC-USDX-PERP\",\"side\":\"Buy\",\"order_type\":\"Limit\",\"quantity\":\"0.1\",\"price\":\"50000\"}`, `x-timestamp: 1776033900123`, `x-nonce: 42`\n- canonical string (LF shown as `⏎`): `POST⏎/orders⏎⏎59ddf9017ca0eb5f8802afd1a2d1584b2d93b0260a0fcd62a1b94b3ff92b332c⏎1776033900123⏎42`\n- digest: `0xe27ade6101c417d2c393abfce8f35b6e1551cf0ce5c50dfbe12f8d6f399ffc35`\n- `x-signature: 0xeef09105834062da10d208be38311995d04cbc5e05043b89e7cbe6d4497d11b51f61729639551a8cfb6ea3e4fe0765afeba7bf3b5f5e09f63bc095c89005b61d1c`\n\n**Network scope.** Like every credential here, an agent registration belongs to the host it was registered on. The canonical string has no network component, so the refusal elsewhere comes from the agent being unknown to that host."}},"schemas":{"DepositTarget":{"description":"Funding instructions for the authenticated account, discriminated on `mode`. `onchain` is returned only by a deployment with a real deposit-contract address configured; every other deployment returns `testnet-faucet`. The mode is a property of the deployment, so a client must branch on it rather than pin one shape.","oneOf":[{"$ref":"#/components/schemas/DepositTargetOnchain"},{"$ref":"#/components/schemas/DepositTargetTestnetFaucet"}],"discriminator":{"propertyName":"mode","mapping":{"onchain":"#/components/schemas/DepositTargetOnchain","testnet-faucet":"#/components/schemas/DepositTargetTestnetFaucet"}}},"DepositTargetOnchain":{"type":"object","description":"Funding instructions for a deployment with an on-chain deposit contract configured (mode `onchain`). Real value moves: the funds are bridged collateral, not synthetic.","required":["mode","account","asset","min_amount","onchain","confirm"],"properties":{"mode":{"type":"string","enum":["onchain"]},"account":{"type":"string","description":"The authenticated account, as `0x` + 40 hex characters. This is whose balance the instructions fund; it is derived from the credential, not from any request parameter."},"asset":{"type":"string","description":"Collateral asset the instructions fund. USDX is the only collateral asset the venue accepts."},"min_amount":{"allOf":[{"$ref":"#/components/schemas/Decimal"}],"description":"Smallest funding amount the venue advises, as a decimal string. **Advisory, not enforced** — `POST /account/credit` enforces only its per-key daily cap, and nothing rejects a smaller on-chain deposit. It is the floor that makes a first trade viable, and it is deployment configuration rather than a contract constant."},"onchain":{"type":"object","description":"The on-chain deposit target.","required":["chain","asset","address","min_amount"],"properties":{"chain":{"type":"string","description":"Chain label the deposit contract lives on. Deployment configuration — read it, do not hardcode it."},"asset":{"type":"string","description":"Asset the contract accepts. Only USDX is accepted; other tokens are rejected on-chain."},"address":{"type":"string","description":"Deposit-contract address, `0x` + 40 hex characters. Always well-formed: a deployment whose configured address is malformed returns `503` rather than publishing it."},"min_amount":{"allOf":[{"$ref":"#/components/schemas/Decimal"}],"description":"Same advisory floor as the top-level `min_amount`."},"instructions":{"type":"string","description":"Human-readable deposit procedure. Diagnostic wording — do not match on it."}}},"confirm":{"$ref":"#/components/schemas/DepositTargetConfirm"}}},"Decimal":{"type":"string","description":"Arbitrary-precision decimal serialized as a string (lossless). Parse with a decimal type, never a float."},"DepositTargetConfirm":{"type":"object","description":"How to confirm the funds arrived. Identical in every mode, and the portable primitive: poll the named path until `poll_field` reflects the credit before trading.","required":["method","path","poll_field"],"properties":{"method":{"type":"string"},"path":{"type":"string","description":"Operation path to poll, relative to the base you are calling."},"poll_field":{"type":"string","description":"Field in that response whose change confirms the funds landed."},"note":{"type":"string","description":"Human-readable guidance. Diagnostic wording — do not match on it."}}},"DepositTargetTestnetFaucet":{"type":"object","description":"Funding instructions for a deployment with no on-chain deposit contract configured (mode `testnet-faucet`). The credit is **synthetic test USDX with no real-world value**, applied off-chain — no on-chain transfer occurs. Do not build a funding flow that assumes this mode exists on every network: mainnet has no faucet.","required":["mode","account","asset","min_amount","faucet","confirm"],"properties":{"mode":{"type":"string","enum":["testnet-faucet"]},"account":{"type":"string","description":"The authenticated account, as `0x` + 40 hex characters. This is whose balance the instructions fund; it is derived from the credential, not from any request parameter."},"asset":{"type":"string","description":"Collateral asset the instructions fund. USDX is the only collateral asset the venue accepts."},"min_amount":{"allOf":[{"$ref":"#/components/schemas/Decimal"}],"description":"Smallest funding amount the venue advises, as a decimal string. **Advisory, not enforced** — `POST /account/credit` enforces only its per-key daily cap, and nothing rejects a smaller on-chain deposit. It is the floor that makes a first trade viable, and it is deployment configuration rather than a contract constant."},"faucet":{"type":"object","description":"The synthetic-credit endpoints to call. `primary` is preferred for autonomous clients — it is per-API-key and takes an amount; `alternate` is a fixed per-wallet grant.","required":["primary","alternate"],"properties":{"primary":{"type":"object","description":"Preferred: `POST /account/credit`, per-API-key and amount-taking.","required":["method","path"],"properties":{"method":{"type":"string"},"path":{"type":"string"},"body":{"type":"object","description":"Request body to send, pre-filled with `min_amount`. Omit `amount` to claim the remaining daily allowance.","additionalProperties":true},"note":{"type":"string","description":"Human-readable guidance. Diagnostic wording — do not match on it."}}},"alternate":{"type":"object","description":"Alternative: `POST /faucet`, a fixed per-wallet grant claimable once per 24h.","required":["method","path"],"properties":{"method":{"type":"string"},"path":{"type":"string"},"note":{"type":"string","description":"Human-readable guidance. Diagnostic wording — do not match on it."}}},"disclaimer":{"type":"string","description":"States that the credit is synthetic and no on-chain transfer occurs. Surface it to a human operator rather than discarding it."}}},"confirm":{"$ref":"#/components/schemas/DepositTargetConfirm"}}},"RateLimitError":{"type":"object","description":"The body of a 429. Branch on `code` (always `RATE_LIMIT_EXCEEDED`) and on `bucket` to learn WHICH budget bottlenecked. Schematised rather than left to `examples` because `bucket` is meant to be read by machines: an example gives a generated client no field and a validator nothing to check `\"bucket\": \"ownr\"` against. `bucket` here and the `X-RateLimit-Bucket` header carry the same value and the same enum.","required":["code","message","bucket"],"properties":{"code":{"type":"string","enum":["RATE_LIMIT_EXCEEDED"],"description":"Always `RATE_LIMIT_EXCEEDED` on this response. The other 429s this API can return carry different codes (`too_many_agents`, `rate_limited`, `cap_exceeded`, `daily_limit_exceeded`) and are not this shape."},"message":{"type":"string","description":"A diagnostic whose wording is NOT stable. Do not parse it; branch on `bucket`."},"bucket":{"type":"string","enum":["key","owner","order","cancel","ip","login"],"description":"Which budget refused this request. `key` — the per-API-key bucket; `owner` — the per-account request bucket; `order` — the trading-action bucket, order submission and amend only; `cancel` — the separate cancellation bucket, `DELETE` on the order surface only; `ip` — the public per-IP bucket for unauthenticated and gateway traffic; `login` — the dedicated per-IP bucket for `POST /auth/login`, tighter than `ip` and drawn from its own pool, so a login refusal leaves the read budget untouched and vice versa. The buckets are independent, so a caller at its read ceiling can still submit orders, and a caller at its submission ceiling can still cancel — do not back off the whole client on any one of them."},"tier":{"type":"string","description":"The rate-limit tier the refused request was charged against — `public` for the per-IP bucket, otherwise the authenticated key's tier. Absent on responses from paths that refuse before a tier is resolved."}}}},"responses":{"Unauthorized":{"description":"Authentication failed. All 401 responses return the same opaque body to prevent information leakage. A credential minted on a different network is one of the causes it hides — by design, so that a key id cannot be probed for existence on another network. Do not retry it against another host.","content":{"application/json":{}}},"RateLimited":{"description":"Rate limit exceeded. **Retryable** — honour `retry-after` and back off; this is what separates a `429` from the permanent `403` jurisdiction refusals. Branch on the body's `code`, which is always `RATE_LIMIT_EXCEEDED`, and on `bucket` to learn WHICH budget bottlenecked — the buckets are independent, so a caller at its read ceiling can still submit orders and should not back off the whole client. Do not parse `message`: it is a diagnostic whose wording is not stable. Requests are charged by weight, so exhausting a budget takes fewer heavy calls than `x-ratelimit-limit` suggests. See “Rate limits” in the API description.","headers":{"X-RateLimit-Limit":{"schema":{"type":"integer"},"description":"Budget of request weight per second for your tier — not a count of requests. Sent on successful responses too."},"X-RateLimit-Remaining":{"schema":{"type":"integer"},"description":"Tokens left, in unit-cost requests: 10 means ten weight-1 requests or two weighing 5. Sent on successful responses too. Always `0` on this response."},"X-RateLimit-Reset":{"schema":{"type":"integer"},"description":"Unix timestamp (seconds) when the budget is whole again. Sent only on a `429`, never on a success."},"Retry-After":{"schema":{"type":"integer"},"description":"Seconds to wait before retrying, never below 1. Derived from the **weighted** cost of the refused request, so it is not in the same unit as `X-RateLimit-Remaining`. Sent only on a `429`."},"X-RateLimit-Bucket":{"schema":{"type":"string","enum":["key","owner","order","cancel","ip","login"]},"description":"Which budget refused this request, mirroring the body's `bucket`. `key` — the per-API-key bucket; `owner` — the per-account request bucket; `order` — the trading-action bucket, order submission and amend only; `cancel` — the separate cancellation bucket, `DELETE` on the order surface only; `ip` — the public per-IP bucket for unauthenticated and gateway traffic; `login` — the dedicated per-IP bucket for `POST /auth/login`, tighter than `ip` and drawn from its own pool, so a login refusal leaves the read budget untouched and vice versa. The read, trading and cancellation budgets are counted separately, so a `429` on one does not mean the others are exhausted — in particular a `429` naming `order` never means your cancels are refused. Sent only on a `429`."}},"content":{"application/json":{"schema":{"$ref":"#/components/schemas/RateLimitError"}}}}}},"paths":{"/account/deposit-target":{"get":{"operationId":"fetchDepositAddress","tags":["Account"],"summary":"How to fund this account","description":"Machine-readable funding instructions for the authenticated account, so an autonomous client can fund itself without out-of-band knowledge of how a given deployment accepts collateral.\n\n**The response is a discriminated union on `mode`, and which mode you get is a property of the deployment, not of the request.** Branch on `mode`; do not assume either shape. A deployment with a real deposit-contract address configured answers `onchain`; otherwise it answers `testnet-faucet` and points at its synthetic-credit endpoints. There is no request parameter that selects between them.\n\nAn address is never fabricated to fill the `onchain` shape. A deployment configured for on-chain deposits whose address is malformed refuses with `503` rather than silently falling back to the faucet, because depositing to a bad address burns the funds.\n\n`confirm` is identical in both modes and is the portable primitive: poll `GET /account` until `balance` reflects the funds.\n\nThis operation is **discovery only**. It moves no funds, creates no deposit, and has no side effect — acting on the returned `faucet` or `onchain` instruction is a separate, explicit step by the caller.","responses":{"200":{"description":"Funding instructions for the authenticated account. Exactly one `mode` is returned; the fields beyond the common ones depend on it.","content":{"application/json":{"schema":{"$ref":"#/components/schemas/DepositTarget"}}}},"401":{"$ref":"#/components/responses/Unauthorized"},"403":{"description":"Refused with `EARLY_ACCESS_REQUIRED`: this deployment restricts funding to early-access participants and the authenticated account is not one. Permanent for that account until it is enrolled — do not retry. The gate deliberately mirrors `POST /account/credit` and `POST /faucet`, so an account that cannot be funded is not told how to fund. Deployments with early access disabled never return it. The contract-wide `RESTRICTED_JURISDICTION` refusal can also surface as a `403` on any operation — see “Jurisdiction restrictions”.","content":{"application/json":{}}},"429":{"$ref":"#/components/responses/RateLimited"},"503":{"description":"`DEPOSIT_TARGET_MISCONFIGURED`: the deployment is configured for on-chain deposits but its deposit-contract address is not a well-formed address, so no funding target can be published. This is an operator misconfiguration rather than a transient fault; retrying does not clear it, and the endpoint deliberately refuses rather than answering `testnet-faucet`, which would mask the bad configuration.","content":{"application/json":{}}}}}}}}
````
**Test it** cannot sign this request. `X-Signature` is an HMAC computed per call: see [Authentication](/api-reference/guides/authentication.md), or use an SDK.
***
API version `0.9.131`
---
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