vocabulary: name: 0x Domain Vocabulary description: >- Domain vocabulary for the 0x liquidity infrastructure platform, covering DEX aggregation, on-chain settlement, gasless meta-transactions, cross-chain bridging, and integrator monetisation concepts. version: '2026-05-28' terms: - term: 0x API definition: >- Unified REST API exposing the 0x liquidity engine. Comprises four product surfaces: Swap, Gasless, Cross-Chain, and Trade Analytics. All endpoints are served from `https://api.0x.org` and authenticated with a `0x-api-key` header plus a `0x-version` header. tags: [Platform, Core Concept] - term: Swap API definition: >- REST API that aggregates 150+ liquidity sources (AMMs + private market makers) and returns indicative prices, firm quotes, and ready-to-sign transaction calldata. Supports two allowance models — AllowanceHolder and Permit2. tags: [Product, Swap] - term: Gasless API definition: >- REST API that lets end users swap tokens without holding the native gas asset. The taker signs an off-chain Permit2 EIP-712 meta-transaction and 0x relayers submit it on-chain. Gas fees are deducted from the sell-side token. tags: [Product, Gasless, Meta-Transactions] - term: Cross-Chain API definition: >- Private-beta REST API that returns aggregated bridge quotes across 16+ providers (Across V4, Relay, Bungee, CCIP, Squid Coral, NEAR Intents, OFT, Mayan, Circle CCTP, Arbitrum, Linea, Superchain, HyperCore) for any-token, any-chain swaps including non-EVM destinations like Solana, HyperCore, and Tron. tags: [Product, Cross-Chain, Bridging] - term: Trade Analytics API definition: >- Read-only REST API that returns the integrator's historical Swap and Gasless trade records — including integrator fee accrual, trade surplus, and on-chain settlement metadata — for monetisation reporting and accounting. tags: [Product, Analytics, Reporting] - term: AllowanceHolder definition: >- Recommended swap allowance flow. The taker grants a one-time ERC-20 approval to the AllowanceHolder contract; subsequent swaps require only a single transaction. Multisig- and smart-account-friendly because it does not require off-chain signature support. tags: [Allowance, Pattern] - term: Permit2 definition: >- Uniswap-standard signature-based allowance system. Replaces individual ERC-20 approvals with EIP-712 signed permits that authorise a single spender for a single amount until a deadline. The advanced 0x flow, used by Swap API v2 and required by the Gasless API. tags: [Allowance, Standard, EIP-712] - term: Settler definition: >- 0x's settlement smart contract — the on-chain target of every Swap API quote's `transaction.to`. The current Settler uses Permit2 for token movement. Integrators MUST NOT set allowances directly on the Settler. tags: [Smart Contract, Settlement] - term: Liquidity Source definition: >- A venue 0x routes against — either a public AMM (Uniswap V3, Curve, Balancer, Maverick, etc.) or a private RFQ market maker. Sources are chain-scoped and can be enabled or disabled per request via `excludedSources` / `includedSources`. tags: [Liquidity, Routing] - term: RFQ (Request-for-Quote) definition: >- Private liquidity channel where professional market makers stream prices to the 0x API. RFQ fills typically beat AMM pricing and avoid revert risk. Included automatically in /price responses regardless of the `taker` parameter. tags: [Liquidity, Private] - term: Trade Surplus definition: >- Positive price improvement that occurs when an order fills better than the quoted price. On the Standard pricing plan, 0x collects the trade surplus as part of its revenue model. tags: [Monetization, Pricing] - term: Integrator Fee (swapFeeBps) definition: >- Optional fee the integrator charges on swap volume, configured by passing `swapFeeBps` and `swapFeeRecipient` query parameters. The fee is deducted on-chain by the Settler and remitted to the recipient address. tags: [Monetization, Fee] - term: Slippage definition: >- The maximum acceptable difference between the quoted buyAmount and the actual fill amount. Controlled by the `slippageBps` query parameter (default 100 bps = 1%). tags: [Trading, Risk] - term: Liquidity Available definition: >- Top-level boolean field on /price and /quote responses indicating whether 0x found a viable route for the requested pair and size. If `liquidityAvailable` is false, no other fields are populated. tags: [API Field] - term: Trade Hash definition: >- Unique 32-byte identifier for a Gasless trade. Returned by POST /gasless/submit and used as the path parameter for GET /gasless/status/{tradeHash}. tags: [Gasless, Identifier] - term: Approval Token definition: >- An ERC-20 token that supports a gasless approval scheme (Permit, Permit2, or ExecuteMetaTransaction). Returned by GET /gasless/gasless-approval-tokens for each supported chain. The Gasless API requires the sell token to be on this list. tags: [Gasless, Token] - term: Bridge Provider definition: >- A cross-chain liquidity provider integrated into the Cross-Chain API. Selected per quote via the `includedBridges` / `excludedBridges` parameters. Provider IDs are documented at docs.0x.org/introduction/supported-chains. tags: [Cross-Chain, Bridging] - term: ChainId definition: >- The numeric identifier of the chain a request applies to. Swap and Gasless support 20+ EVM chains using canonical EVM chain IDs. The Cross-Chain API also uses virtual chain IDs for non-EVM destinations: Solana = 999,999,999,991; HyperCore = 999,999,999,992; Tron = 999,999,999,993. tags: [Chain, Identifier] - term: 0x Settler Contract definition: >- The on-chain Solidity contract suite (0xProject/0x-settler) that receives and executes every swap. Built around Permit2 and audited for the v2 release. Source published at github.com/0xProject/0x-settler. tags: [Smart Contract, Settlement] - term: Matcha definition: >- 0x's consumer-facing aggregator UI (matcha.xyz). A reference integration of the Swap and Cross-Chain APIs. tags: [Product, Consumer] - term: 0x Dashboard definition: >- The integrator self-service portal at dashboard.0x.org for creating API keys, viewing usage, managing billing, and configuring fee recipients. tags: [Portal, Integrator] - term: 0x MCP Server definition: >- Hosted Model Context Protocol server at `https://docs.0x.org/_mcp/server` that gives AI agents live, searchable access to 0x documentation. tags: [AI, Tooling] - term: 0x Agent Skill (0x-api) definition: >- Official Claude Code / Cursor / GitHub Copilot Agent Skill installed via `npx skills add 0xProject/0x-ai`. Embeds 0x API knowledge into the agent so it can generate production-ready swap and gasless code. tags: [AI, Tooling] maintainer: name: Kin Lane email: kin@apievangelist.com