> ## Documentation Index > Fetch the complete documentation index at: https://docs.hex-api.app/llms.txt > Use this file to discover all available pages before exploring further. # Pay out a receiver's pending withdrawals > Queues paying out **every** pending withdrawal of `receiver` on `chain_id` and answers the job. Poll it with `GET /relay/jobs/{chain}/{id}`. One job per receiver drains omni's `get_withdrawals_by_receiver` oldest first, one withdrawal at a time: an unpaid one is signed and sent to the chain's bridge (`withdraw`) from the relay's account, which pays the fees; a paid one is cleared on omni (`clear_completed_withdrawal`). It is done when omni lists none. A signing refusal fails the job with its detail; RPC and node failures are retried with backoff. A withdrawal to the token contract itself or to the zero address is never paid out, nor a Stellar one older than the bridge's 60-day nonce lifetime (it can only be refunded). Chains the relay pays out on: EVM chains except Ethereum (1), Base (8453), Linea (59144), Mantle (5000) and Abstract (2741); Gonka (4444119), Stellar (1100) and TON (1117). A chain is also refused (400) while omni's removal key for it is neither the MPC key nor the one this service holds, since a payout it could not clear would block the receiver's next withdrawals. Only a receiver omni holds a withdrawal for is queued: otherwise `404`, and nothing is queued. A receiver with a queued or running job answers that job (`reused: "active"`) instead of a new one; within 2 minutes of a job of the receiver that failed, or that already went past the withdrawal asked for (or found nothing), that job is answered too (`reused: "cooldown"`). A chain's payout queue holds at most 500 jobs per shard: past it, `429` with `Retry-After`. ## OpenAPI ````yaml https://mpc.hex-api.app/openapi.json post /relay/withdraw openapi: 3.1.0 info: title: HEX MPC API version: 1.0.0 summary: HOT bridge signatures and relay, the bridge registry and monitor. description: > The public API of `hex-mpc`, a Cloudflare Worker in front of the HOT MPC nodes. It replaces the old HOT backend's bridge endpoints (`api0.herewallet.app`: `process_bridge_deposit`, `auto_deposit_register`, ...) and HOR (`rpc1.hotdao.ai`, `rpc2.hotdao.ai`). ## Which routes to use - **Credit a deposit to NEAR Intents**: `POST /relay/deposit` with the source tx (or the deposit's fields). The service reads the deposit on its chain, signs it and sends `mt_deposit_call` on NEAR, paying the gas. This is what `process_bridge_deposit` did. - **Pay out withdrawals**: `POST /relay/withdraw` with the chain and the receiver; poll `GET /relay/jobs/{chain}/{id}`. - **Clear a paid withdrawal**: `POST /relay/clear`. - **Submit transactions yourself**: the `Signatures` routes return the MPC signatures only. - **Record what your users do** (optional, for support and recovery): `POST /bridge/register`, `/bridge/deposits`, `/bridge/withdrawals`. Every relay call sends only what holds on chain (a deposit that happened, the payout of a withdrawal omni holds, the clear of a paid one), and each at most once, so retrying a call is safe. ## Conventions - **Bodies** are JSON objects, at most 32 KiB (`/intents/solver`: 128 KiB). A body that is not a JSON object is a `422`, a larger one a `413`. - **Big integers.** Nonces and amounts are answered as decimal strings. In requests they may be decimal strings or JSON integers: integers above 2^53 are read exactly (the bridge's nonces are about 1.8e21), but a decimal string is the safer choice for clients whose JSON encoder uses doubles. - **Nonces** are omni's: `unix seconds * 10^12 + n`. - **Encodings.** omni's token ids, receivers and the bridge signatures are base58; NEAR tx hashes are base58. - **Chain ids.** Chain ids are omni's (`v2_1.omni.hot.tg`), not always the chain's own: EVM chains use their EIP-155 id (Ethereum 1, Optimism 10, BNB 56, Polygon 137, Monad 143, X Layer 196, Base 8453, Arbitrum 42161, Avalanche 43114, ...); the others have omni's numbers: Solana 1001, NEAR 1010, Stellar 1100, TON 1117 (TON v1, 1111, is dead), Juno 4444118, Gonka 4444119. - **Errors** are `{ "detail": "..." }` with an HTTP status (FastAPI's format, kept from HOR), the router's own `404`, `405` and `429` included. Clients should branch on the status and show or log the `detail`. A `5xx` (and a `502`/`503` in particular) is worth retrying with backoff; a `4xx` will answer the same until something changes on chain. - **CORS.** Any origin; the request's `Origin` is echoed with `access-control-allow-credentials: true`, and preflights allow `GET, POST, OPTIONS` with any header. - **Times** in answers are milliseconds since the epoch unless named `*_s` (seconds). ## Rate limits Per client IP (an IPv6 client by its /64), over 60 seconds, counted per Cloudflare location: | Class | Limit | Routes | | --- | --- | --- | | `bridge` | 300 / 60 s | `/withdraw/sign`, `/deposit/sign`, `/clear/sign`, `/relay/*`, `/bridge/*` | | `solver` | 120 / 60 s | `/intents/solver` | `/v1/health`, `/v1/time` and `/openapi.json` are not limited. Over the limit the answer is `429` `{ "detail": "Too many requests" }` with `Retry-After: 60`. ## Load protection The MPC nodes are a fixed quorum: every signature is a round on each of them. So on top of the per-IP limits, every call that reaches the nodes (the `Signatures` routes, and the relay's own signing) is admitted globally, whoever asks: - **Rate per kind of signing**, by default 300 a minute each for withdrawals, deposits and clears: over it, `429` with `Retry-After`. - **Signings at once**, 60 in all, each kind its own share: over it, `503` `MPC nodes are busy, try again shortly` with `Retry-After`. Also `503` with `Retry-After` when the nodes answer `429` or too few of them are up. - **One signing per message.** A signature is kept for a day and answered again (a retry, another client, the relay), and while it is being made a second request waits for it (or gets `503` `This signature is being made, try again shortly` after 45 s). A refusal of the bridge (`400`) is answered again for 5 seconds. - **Refusals before the nodes**: a deposit omni already credited (`400` `Deposit … is already credited`), a withdrawal no payout can land (`400` `Withdrawal … : it can only be refunded`: it pays the token contract itself, the zero address, or a Stellar nonce past its 60 days). Retry a `429` or `503` after its `Retry-After`. servers: - url: https://mpc.hex-api.app description: Production security: [] tags: - name: Relay description: >- The recommended integration: the service sends the bridge's transactions and pays for them. Deposits are credited to NEAR Intents; withdrawals are paid out on their chain and cleared on omni. - name: Signatures description: >- The bridge's MPC signatures, for callers that submit the transactions themselves (HOR-compatible: same bodies, answers and errors). Each signature needs omni's word, and a deposit or clear also its AuthCall on chain, so a caller cannot forge or redirect one. - name: Registry description: >- The bridge registry: what users do on the bridge, as clients report it and as the relay sees it on chain. A post only records a claim: nothing is signed or sent for it, and what the relay reads on chain overrides it. Lookups answer 503 while the registry's database is not configured. - name: Monitor description: Health of every bridge HEX moves funds through, over 24 hours. - name: Intents description: >- NEAR Intents solver relay passthrough, used by HEX/HOT kit to publish signed intents. - name: Service description: Health, time and this document. paths: /relay/withdraw: post: tags: - Relay summary: Pay out a receiver's pending withdrawals description: >- Queues paying out **every** pending withdrawal of `receiver` on `chain_id` and answers the job. Poll it with `GET /relay/jobs/{chain}/{id}`. One job per receiver drains omni's `get_withdrawals_by_receiver` oldest first, one withdrawal at a time: an unpaid one is signed and sent to the chain's bridge (`withdraw`) from the relay's account, which pays the fees; a paid one is cleared on omni (`clear_completed_withdrawal`). It is done when omni lists none. A signing refusal fails the job with its detail; RPC and node failures are retried with backoff. A withdrawal to the token contract itself or to the zero address is never paid out, nor a Stellar one older than the bridge's 60-day nonce lifetime (it can only be refunded). Chains the relay pays out on: EVM chains except Ethereum (1), Base (8453), Linea (59144), Mantle (5000) and Abstract (2741); Gonka (4444119), Stellar (1100) and TON (1117). A chain is also refused (400) while omni's removal key for it is neither the MPC key nor the one this service holds, since a payout it could not clear would block the receiver's next withdrawals. Only a receiver omni holds a withdrawal for is queued: otherwise `404`, and nothing is queued. A receiver with a queued or running job answers that job (`reused: "active"`) instead of a new one; within 2 minutes of a job of the receiver that failed, or that already went past the withdrawal asked for (or found nothing), that job is answered too (`reused: "cooldown"`). A chain's payout queue holds at most 500 jobs per shard: past it, `429` with `Retry-After`. operationId: relayWithdraw requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/RelayWithdrawRequest' examples: polygon: summary: An EVM receiver value: chain_id: 137 receiver: '0xe4df1d74122c2a7b14481cbdde704fbd0a4f11a2' stellar: summary: A Stellar receiver, in omni's base58 value: chain_id: 1100 receiver: 1114wxgAxsZMgcitQaVJLFGp4U8ZgJTtC6wgFMt2pu4tEXU1bzbfMaiEDiw responses: '200': description: 'The receiver''s job: new, or the active one.' content: application/json: schema: $ref: '#/components/schemas/EnqueueAnswer' examples: queued: summary: A new job value: id: 3.b55dd9d2-a1bd-48fb-b8d6-6e91aa21433b origin: api chain_id: 137 receiver: 4BwLMDn4SNyrgHHgU9x5tAudyGZ7 status: queued steps: [] created_at: 1792944180000 updated_at: 1792944180000 active: summary: The receiver already has one value: id: 3.b55dd9d2-a1bd-48fb-b8d6-6e91aa21433b origin: api chain_id: 137 receiver: 4BwLMDn4SNyrgHHgU9x5tAudyGZ7 status: running pending: 2 steps: [] detail: >- withdraw 0xdfd90cb908815115b944a21f71a015cccfe668ff8752e49d440beb9da7769df4 of 1792107257000001836156 is pending created_at: 1792944180000 updated_at: 1792944184000 reused: active '400': description: The chain is not relayed. content: application/json: schema: $ref: '#/components/schemas/Error' examples: unrelayed: value: detail: >- Chain 8453 withdrawals are not relayed: not served by the relay clears: value: detail: >- Chain 56 withdrawals are not relayed: its clears cannot be signed here notRelayed: value: detail: Chain 1001 withdrawals are not relayed '404': description: omni holds no withdrawal to the receiver on the chain. content: application/json: schema: $ref: '#/components/schemas/Error' examples: none: value: detail: >- No pending withdrawal to 0xe4df1d74122c2a7b14481cbdde704fbd0a4f11a2 on chain 137 '413': $ref: '#/components/responses/PayloadTooLarge' '422': description: A malformed field. content: application/json: schema: $ref: '#/components/schemas/Error' examples: chain: value: detail: chain_id must be a chain id evm: value: detail: receiver must be an EVM address other: value: detail: receiver is not an address of chain 1100 '429': description: Over the per-IP rate limit, or the chain's payout queue is full. headers: Retry-After: $ref: '#/components/headers/RetryAfter' content: application/json: schema: $ref: '#/components/schemas/Error' examples: limited: value: detail: Too many requests full: value: detail: The withdraw relay of chain 137 is full, try again later '500': $ref: '#/components/responses/InternalError' '502': $ref: '#/components/responses/BadGateway' '503': $ref: '#/components/responses/ServiceUnavailable' components: schemas: RelayWithdrawRequest: type: object required: - chain_id - receiver properties: chain_id: $ref: '#/components/schemas/ChainId' description: >- The target chain. Chains the relay pays out on: EVM chains except Ethereum (1), Base (8453), Linea (59144), Mantle (5000) and Abstract (2741); Gonka (4444119), Stellar (1100) and TON (1117). A chain is also refused (400) while omni's removal key for it is neither the MPC key nor the one this service holds, since a payout it could not clear would block the receiver's next withdrawals. receiver: type: string description: >- The withdrawals' receiver: on EVM a `0x` address or omni's base58 of its 20 bytes; on Gonka a bech32 address or omni's base58; on Stellar and TON omni's base58 (as `get_withdrawals_by_receiver` names it). examples: - '0xe4df1d74122c2a7b14481cbdde704fbd0a4f11a2' EnqueueAnswer: allOf: - $ref: '#/components/schemas/DrainJob' - type: object properties: reused: type: string enum: - active - cooldown description: >- Set when no new job was made: `active`, the receiver's queued or running job; `cooldown`, its last job, finished within 2 minutes (failed, or already past the withdrawal asked for), or for the refuel sweep within its longer cooldown. Error: type: object description: 'Every error: FastAPI''s `{ detail }` with the HTTP status.' required: - detail properties: detail: type: string description: What went wrong, readable. examples: - detail: Nonce was not used on target chain ChainId: type: integer minimum: 1 description: >- Chain ids are omni's (`v2_1.omni.hot.tg`), not always the chain's own: EVM chains use their EIP-155 id (Ethereum 1, Optimism 10, BNB 56, Polygon 137, Monad 143, X Layer 196, Base 8453, Arbitrum 42161, Avalanche 43114, ...); the others have omni's numbers: Solana 1001, NEAR 1010, Stellar 1100, TON 1117 (TON v1, 1111, is dead), Juno 4444118, Gonka 4444119. examples: - 1100 - 1117 - 137 - 4444119 DrainJob: type: object required: - id - origin - chain_id - receiver - status - steps - created_at - updated_at properties: id: type: string description: '`.`, or a bare uuid.' origin: type: string enum: - api - refuel description: >- `api`: `POST /relay/withdraw`. `refuel`: the service's own sweep of stuck withdrawals. chain_id: $ref: '#/components/schemas/ChainId' receiver: $ref: '#/components/schemas/Base58' description: The receiver as omni keeps it (base58 of its bytes). status: type: string enum: - queued - running - done - failed pending: type: integer minimum: 0 description: >- The receiver's pending withdrawals at the last step. Absent before the first. steps: type: array items: $ref: '#/components/schemas/DrainStep' detail: type: string description: Why it failed, or what it is waiting for. created_at: type: integer description: ms. updated_at: type: integer description: ms. Base58: type: string pattern: ^[1-9A-HJ-NP-Za-km-z]+$ description: Base58 (Bitcoin alphabet). DrainStep: type: object required: - nonce - action - tx - at properties: nonce: $ref: '#/components/schemas/NonceString' action: type: string enum: - withdraw - clear description: >- `withdraw`: the payout sent on the target chain. `clear`: `clear_completed_withdrawal` on NEAR. tx: type: string description: >- The tx (or, on EVM through the smart wallet, the call id) of the step. at: type: integer description: When, ms. NonceString: type: string pattern: ^\d{1,39}$ description: omni's nonce (`unix seconds * 10^12 + n`), decimal. examples: - '1792944123000000004211' responses: PayloadTooLarge: description: 'The body exceeds 32 KiB (`/intents/solver`: 128 KiB).' content: application/json: schema: $ref: '#/components/schemas/Error' examples: tooLarge: value: detail: Body exceeds 32768 bytes InternalError: description: An unexpected error. Its message is not exposed. content: application/json: schema: $ref: '#/components/schemas/Error' examples: internal: value: detail: Internal Server Error BadGateway: description: >- A chain or NEAR RPC is unavailable, or an answer could not be read. Retry with backoff. content: application/json: schema: $ref: '#/components/schemas/Error' examples: near: value: detail: NEAR RPC is unavailable, try again chain: value: detail: Stellar RPC of chain 1100 is unavailable, try again ServiceUnavailable: description: Something the route needs is not configured on the service. content: application/json: schema: $ref: '#/components/schemas/Error' examples: nodes: value: detail: MPC nodes are not configured relay: value: detail: The relay's NEAR keys are not configured headers: RetryAfter: description: Seconds to wait. schema: type: integer example: 60 ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.