# BRRR Developer Docs > Explore our API & SDK references, demos, and guides for building payment flows. ## Table of Contents - [Examples - BRRR Developer Docs](https://docs.brrr.network/docs/examples.md): Explore BRRR examples with live demos and source code for wagmi, ethers.js, web3.js, and Solana. - [Changelog - BRRR Developer Docs](https://docs.brrr.network/docs/changelog.md): Release notes and recent changes across the APIs, SDK, and Payments for AI Agents API. #### Get Started - [Develop with AI - BRRR Developer Docs](https://docs.brrr.network/docs/develop-with-ai.md): Use AI coding assistants to build BRRR integrations faster with llms.txt and ready-made system prompts. - [Supported Networks - BRRR Developer Docs](https://docs.brrr.network/docs/supported-networks.md): This page provides an overview of the blockchain networks we currently support. - [Supported Regions - BRRR Developer Docs](https://docs.brrr.network/docs/supported-regions.md): This page provides an overview of the countries where each BRRR feature is available. - [FAQ - BRRR Developer Docs](https://docs.brrr.network/docs/faq.md): Answers to common questions about the BRRR APIs and SDK. - [Testing - BRRR Developer Docs](https://docs.brrr.network/docs/testing.md): Test your BRRR SDK integration safely with the $SDKTEST holytag. - [Go-Live Checklist - BRRR Developer Docs](https://docs.brrr.network/docs/go-live.md): A production readiness checklist to verify your BRRR integration is correctly configured before going live. #### Core concepts - [Deposit - BRRR Developer Docs](https://docs.brrr.network/docs/off-ramp.md): Move tokens from a user's wallet into EUR on a Holyheld card. The SDK handles user-facing flows; the APIs handle server-side settlement. - [Withdraw - BRRR Developer Docs](https://docs.brrr.network/docs/on-ramp.md): Spend EUR from a Holyheld card and deliver tokens to a wallet. The user confirms in the Holyheld mobile app within 3 minutes. - [Orchestrate - BRRR Developer Docs](https://docs.brrr.network/docs/orchestration.md): The supporting layer that makes Deposits and Withdraws work — cross-chain routing, address validation, balance lookup, and monitoring. #### APIs - [APIs - BRRR Developer Docs](https://docs.brrr.network/docs/api/introduction.md): Overview of the BRRR API surface: products, environments, and request conventions. - [API Authentication - APIs - BRRR Developer Docs](https://docs.brrr.network/docs/api/authentication.md): How to authenticate requests using your API key. - [API Sections - BRRR Developer Docs](https://docs.brrr.network/docs/api/sections.md): Overview of the four BRRR API products with flow diagrams and endpoint tables. - [Webhooks - BRRR Developer Docs](https://docs.brrr.network/docs/api/webhooks.md): Receive event notifications from Holyheld. #### Multi-tenant Settlement - [Onboarding - Multi-tenant Settlement - BRRR Developer Docs](https://docs.brrr.network/docs/settlement/onboarding.md): Register customers and associate their EVM addresses. - [Offboarding - Multi-tenant Settlement - BRRR Developer Docs](https://docs.brrr.network/docs/settlement/offboarding.md): Remove customers or wallet addresses from monitoring. - [Risk assessment - Multi-tenant Settlement - BRRR Developer Docs](https://docs.brrr.network/docs/settlement/risk-assessment.md): Risk assessment process and webhook notifications. - [Monitoring - Multi-tenant Settlement - BRRR Developer Docs](https://docs.brrr.network/docs/settlement/monitoring.md): How address monitoring works and when risk re-evaluations are triggered. - [Settlement estimation - Multi-tenant Settlement - BRRR Developer Docs](https://docs.brrr.network/docs/settlement/settlement-estimation.md): Request settlement quotes before executing settlement. - [Settlement execution - Multi-tenant Settlement - BRRR Developer Docs](https://docs.brrr.network/docs/settlement/settlement-execution.md): Execute settlements using a previously generated quote. - [Rates - Multi-tenant Settlement - BRRR Developer Docs](https://docs.brrr.network/docs/settlement/rates.md): Retrieve the current token to fiat exchange rate. #### Agentic payments - [Payments for AI Agents - BRRR Developer Docs](https://docs.brrr.network/docs/agentic/introduction.md): Give your AI agent a spending card. Let agents check balance, retrieve card details, and top up a Holyheld card autonomously with a simple HTTP API. - [Authentication - Agentic payments - BRRR Developer Docs](https://docs.brrr.network/docs/agentic/authentication.md): How to authenticate AI agent requests using the Bearer token included in Holyheld agent instructions. - [Get Balance - Agentic payments - BRRR Developer Docs](https://docs.brrr.network/docs/agentic/get-balance.md): Query the available EUR balance on the Holyheld card. GET /balance endpoint reference. - [Get Card Data - Agentic payments - BRRR Developer Docs](https://docs.brrr.network/docs/agentic/card-data.md): Retrieve Holyheld card details for agent-driven checkout flows. GET /card-data endpoint reference. - [Top Up Card - Agentic payments - BRRR Developer Docs](https://docs.brrr.network/docs/agentic/topup.md): Request a card top-up by transferring funds from the Holyheld main account to the card. POST /topup-request endpoint reference with async polling pattern. - [Error Reference - Agentic payments - BRRR Developer Docs](https://docs.brrr.network/docs/agentic/errors.md): Complete reference for all Payments for AI Agents API error codes, with recovery strategies for each. - [Build an MCP Server - Agentic payments - BRRR Developer Docs](https://docs.brrr.network/docs/agentic/mcp-guide.md): Step-by-step guide to building a Claude MCP server that exposes Holyheld balance, card data, and top-up as native AI tools. - [Agent Patterns - Agentic payments - BRRR Developer Docs](https://docs.brrr.network/docs/agentic/agent-patterns.md): Best practices and common patterns for building reliable AI agents with the Payments for AI Agents API — threshold top-up, safe polling, error escalation, and anti-patterns to avoid. #### Use Cases - [Fintechs - Use Cases - BRRR Developer Docs](https://docs.brrr.network/docs/use-cases/fintechs.md): How consumer fintechs, neobanks, and payment apps embed Deposits and Withdraws — connecting user wallets to a Holyheld card or to the fintech's own settlement rails. - [Web3 - Use Cases - BRRR Developer Docs](https://docs.brrr.network/docs/use-cases/web3.md): How dApps, wallet apps, and on-chain protocols add fiat rails — letting users cash out tokens to a Holyheld card, or fund a wallet from a card balance, without ever touching the user's keys. - [AI Platforms - Use Cases - BRRR Developer Docs](https://docs.brrr.network/docs/use-cases/ai-platforms.md): How agent frameworks (Claude MCP, LangChain, custom) let an AI act on a user's Holyheld card autonomously — checking balance, retrieving card details for checkout, and topping up within a budget. - [BaaS - Use Cases - BRRR Developer Docs](https://docs.brrr.network/docs/use-cases/baas.md): How regulated banking-as-a-service platforms, treasury products, and OTC desks settle crypto to EUR for their own KYC'd customers — server-to-server, with risk scanning and SEPA delivery built in. #### BRRR - [What is BRRR - BRRR Developer Docs](https://docs.brrr.network/docs/what-is-brrr.md): What is BRRR token. - [BRRR Details - BRRR Developer Docs](https://docs.brrr.network/docs/brrr-details.md): Onchain contract details. - [Distribution - BRRR Developer Docs](https://docs.brrr.network/docs/distribution.md): How is the token distributed. - [Emission - BRRR Developer Docs](https://docs.brrr.network/docs/emission.md): Dynamic emission curve. - [Validation - BRRR Developer Docs](https://docs.brrr.network/docs/validation.md): What is it? And how to participate. - [Risk Disclosures - BRRR Developer Docs](https://docs.brrr.network/docs/risk-disclosures.md): Learn about risks involved. - [Examples - BRRR Developer Docs](https://docs.brrr.network/docs/examples.md): Explore BRRR examples with live demos and source code for wagmi, ethers.js, web3.js, and Solana. - [Changelog - BRRR Developer Docs](https://docs.brrr.network/docs/changelog.md): Release notes and recent changes across the APIs, SDK, and Payments for AI Agents API. #### Web3 API - [Get Tag Info - Web3 API - BRRR Developer Docs](https://docs.brrr.network/api/web3/get-tag-info.md): Resolve a Holyheld tag to its public display information. - [Get Token Information - Web3 API - BRRR Developer Docs](https://docs.brrr.network/api/web3/get-token-info.md): Get token metadata with current price for a token on a given network. - [Get Token Metadata - Web3 API - BRRR Developer Docs](https://docs.brrr.network/api/web3/get-token-metadata.md): Retrieve extended token market data and additional visual metadata. - [Get Token Chart - Web3 API - BRRR Developer Docs](https://docs.brrr.network/api/web3/get-token-chart.md): Retrieve historical token price chart data for a selected range. - [Get EVM Balances - Web3 API - BRRR Developer Docs](https://docs.brrr.network/api/web3/get-evm-balances.md): Retrieve all EVM token balances held by a wallet address. - [Get Solana Balances - Web3 API - BRRR Developer Docs](https://docs.brrr.network/api/web3/get-solana-balances.md): Retrieve all Solana token balances held by a wallet address. - [Get Solana Priority Fee - Web3 API - BRRR Developer Docs](https://docs.brrr.network/api/web3/get-solana-priority-fee.md): Retrieve the recommended Solana priority fee for transactions. #### Multi-tenant Settlement API ##### Partner Onboarding - [Register a customer - Multi-tenant Settlement API - BRRR Developer Docs](https://docs.brrr.network/api/settlement/onboarding/register-customer.md): Register a customer and associate their EVM wallet address. - [Add address to a customer - Multi-tenant Settlement API - BRRR Developer Docs](https://docs.brrr.network/api/settlement/onboarding/add-address-to-customer.md): Add an additional EVM wallet address to an existing customer. ##### Partner IBAN - [Add IBAN to a customer - Multi-tenant Settlement API - BRRR Developer Docs](https://docs.brrr.network/api/settlement/iban/add-iban-to-customer.md): Register a SEPA IBAN for an existing partner customer. - [Remove IBAN from a customer - Multi-tenant Settlement API - BRRR Developer Docs](https://docs.brrr.network/api/settlement/iban/remove-iban-from-customer.md): Remove a previously registered IBAN from a partner customer. ##### Partner Customer Info - [Get customer info - Multi-tenant Settlement API - BRRR Developer Docs](https://docs.brrr.network/api/settlement/customer-info/get-customer-info.md): Retrieve a customer's registered EVM addresses and IBANs. ##### Partner Offboarding - [Remove a customer - Multi-tenant Settlement API - BRRR Developer Docs](https://docs.brrr.network/api/settlement/offboarding/remove-customer.md): Remove a customer and all associated wallet addresses from monitoring. - [Remove an address - Multi-tenant Settlement API - BRRR Developer Docs](https://docs.brrr.network/api/settlement/offboarding/remove-address.md): Remove a specific wallet address from monitoring. ##### Partner Risk - [Get risk by customer ID - Multi-tenant Settlement API - BRRR Developer Docs](https://docs.brrr.network/api/settlement/risk-assessment/get-risk-by-customer-id.md): Retrieve risk history for all wallet addresses associated with a customer. - [Get risk by address - Multi-tenant Settlement API - BRRR Developer Docs](https://docs.brrr.network/api/settlement/risk-assessment/get-risk-by-address.md): Retrieve risk status for a specific wallet address. ##### Partner Quote - [Create a settlement quote - Multi-tenant Settlement API - BRRR Developer Docs](https://docs.brrr.network/api/settlement/settlement-estimation/create-settlement-quote.md): Create a settlement quote required for settlement execution. ##### Partner Execution - [Execute settlement - Multi-tenant Settlement API - BRRR Developer Docs](https://docs.brrr.network/api/settlement/settlement-execution/execute-settlement.md): Confirm a settlement quote and initiate settlement execution. - [Get settlement status - Multi-tenant Settlement API - BRRR Developer Docs](https://docs.brrr.network/api/settlement/settlement-execution/get-settlement-status.md): Retrieve the current status of a settlement. ##### Partner Rates - [Get exchange rate - Multi-tenant Settlement API - BRRR Developer Docs](https://docs.brrr.network/api/settlement/rates/get-exchange-rate.md): Retrieve the current token to fiat exchange rate for a token on a specific network. #### OTC API - [Get Sell Crypto Quote - OTC API - BRRR Developer Docs](https://docs.brrr.network/api/otc/otc-sell-crypto-quote.md): Quote a crypto-to-EUR OTC trade. - [Get Buy EUR Quote - OTC API - BRRR Developer Docs](https://docs.brrr.network/api/otc/otc-buy-eur-quote.md): Quote an EUR-to-crypto OTC trade. - [Execute Sell Crypto - OTC API - BRRR Developer Docs](https://docs.brrr.network/api/otc/otc-sell-crypto-execute.md): Confirm a sell-crypto OTC quote and begin execution. - [Execute Buy EUR - OTC API - BRRR Developer Docs](https://docs.brrr.network/api/otc/otc-buy-eur-execute.md): Confirm a buy-EUR OTC quote and begin execution. - [Get OTC Order Status - OTC API - BRRR Developer Docs](https://docs.brrr.network/api/otc/otc-get-order-status.md): Retrieve current status and details for an OTC order. #### Card API ##### Config & Info - [Address Check - Card API - BRRR Developer Docs](https://docs.brrr.network/api/card-api/config-and-info/card-address-check.md): Check whether a wallet address is eligible for Card API onramp and offramp flows. - [Get Buying Rate - Card API - BRRR Developer Docs](https://docs.brrr.network/api/card-api/config-and-info/card-get-buying-rate.md): Retrieve the informational USD/EUR FX rate used in Card API UX. - [Get Configuration - Card API - BRRR Developer Docs](https://docs.brrr.network/api/card-api/config-and-info/card-get-configuration.md): Retrieve Card API network, token, and contract configuration. ##### Offramp - Crypto to Card - [Get Tag Hash - Card API - BRRR Developer Docs](https://docs.brrr.network/api/card-api/offramp-crypto-to-card/card-get-tag-hash.md): Generate a one-time tag hash for crypto-to-card offramp flows. - [EVM Token to EUR Conversion - Card API - BRRR Developer Docs](https://docs.brrr.network/api/card-api/offramp-crypto-to-card/card-evm-convert-token-to-eur.md): Estimate an EVM offramp using a token-denominated amount. - [EVM EUR to Token Conversion - Card API - BRRR Developer Docs](https://docs.brrr.network/api/card-api/offramp-crypto-to-card/card-evm-convert-eur-to-token.md): Estimate an EVM offramp using an EUR-denominated amount. - [Solana Token to EUR Conversion - Card API - BRRR Developer Docs](https://docs.brrr.network/api/card-api/offramp-crypto-to-card/card-solana-convert-token-to-eur.md): Estimate a Solana offramp using a token-denominated amount. - [Solana EUR to Token Conversion - Card API - BRRR Developer Docs](https://docs.brrr.network/api/card-api/offramp-crypto-to-card/card-solana-convert-eur-to-token.md): Estimate a Solana offramp using an EUR-denominated amount. - [Get Transaction Data - Card API - BRRR Developer Docs](https://docs.brrr.network/api/card-api/offramp-crypto-to-card/card-get-transaction-data.md): Build ready-to-broadcast transaction data for a crypto-to-card offramp. - [Execute Gasless Transaction - Card API - BRRR Developer Docs](https://docs.brrr.network/api/card-api/offramp-crypto-to-card/card-execute-gasless-transaction.md): Execute a gasless crypto-to-card offramp on behalf of the customer. ##### Offramp - SEPA Transfers - [Estimate SEPA Fee - Card API - BRRR Developer Docs](https://docs.brrr.network/api/card-api/offramp-sepa-transfers/card-estimate-sepa-fee.md): Estimate the fee for a Card API SEPA transfer. - [Create SEPA Transfer - Card API - BRRR Developer Docs](https://docs.brrr.network/api/card-api/offramp-sepa-transfers/card-create-sepa-transfer.md): Create a one-time SEPA transfer destination for an offramp. ##### Get Offramp Status - [Get Offramp Status - Card API - BRRR Developer Docs](https://docs.brrr.network/api/card-api/offramp-status/card-get-offramp-status.md): Poll the status of a Card API offramp using tag hash, tx hash, or HHTXID. ##### Buy Crypto (Onramp) - [Get Tokens List - Card API - BRRR Developer Docs](https://docs.brrr.network/api/card-api/buy-crypto-onramp/card-get-tokens-list.md): List available Card API onramp tokens for a network. - [Get Token Amount - Card API - BRRR Developer Docs](https://docs.brrr.network/api/card-api/buy-crypto-onramp/card-get-token-amount.md): Estimate token output for a given EUR amount in Card API onramp. - [Get EUR Amount - Card API - BRRR Developer Docs](https://docs.brrr.network/api/card-api/buy-crypto-onramp/card-get-eur-amount.md): Estimate EUR cost for a given token amount in Card API onramp. - [Estimate Onramp Transaction - Card API - BRRR Developer Docs](https://docs.brrr.network/api/card-api/buy-crypto-onramp/card-estimate-onramp-transaction.md): Estimate fees and output for a Card API onramp transaction. - [Execute Onramp - Card API - BRRR Developer Docs](https://docs.brrr.network/api/card-api/buy-crypto-onramp/card-execute-onramp.md): Create a Card API onramp transaction and return its HHTXID. - [Get Onramp Status - Card API - BRRR Developer Docs](https://docs.brrr.network/api/card-api/buy-crypto-onramp/card-get-onramp-status.md): Poll the status of a Card API onramp transaction. - [Examples - BRRR Developer Docs](https://docs.brrr.network/docs/examples.md): Explore BRRR examples with live demos and source code for wagmi, ethers.js, web3.js, and Solana. - [Changelog - BRRR Developer Docs](https://docs.brrr.network/docs/changelog.md): Release notes and recent changes across the APIs, SDK, and Payments for AI Agents API. - [References - SDK - BRRR Developer Docs](https://docs.brrr.network/sdk/references.md): Complete reference for all BRRR SDK functions. #### Get Started - [SDK - BRRR Developer Docs](https://docs.brrr.network/sdk/introduction.md): BRRR SDK provides methods to on-ramp and off-ramp crypto in TypeScript/JavaScript environments. The process takes only a few steps and allows you to customize the customer flow and UI. - [Installation - SDK - BRRR Developer Docs](https://docs.brrr.network/sdk/installation.md): How to install BRRR SDK. - [Initialization - SDK - BRRR Developer Docs](https://docs.brrr.network/sdk/initialization.md): How to initialize the Holyheld SDK with your API key. - [Web3 Providers - SDK - BRRR Developer Docs](https://docs.brrr.network/sdk/web3-providers.md): How to work with different Web3 providers for various blockchain networks. - [Error handling - SDK - BRRR Developer Docs](https://docs.brrr.network/sdk/error-handling.md): Handle HolyheldSDKError exceptions by error code, with cause and recommended action for every error code in the SDK. #### References - [TypeScript Types - SDK - BRRR Developer Docs](https://docs.brrr.network/sdk/references/types.md): Complete reference for all exported TypeScript types, interfaces, and enums in the Holyheld SDK. ##### Off-ramp - [convertTokenToEUR (Off-Ramp) - SDK - BRRR Developer Docs](https://docs.brrr.network/sdk/references/off-ramp/convert-token-to-eur.md): Get a EUR quote for a given token amount — step 3 of the off-ramp flow. - [convertEURToToken (Off-Ramp) - SDK - BRRR Developer Docs](https://docs.brrr.network/sdk/references/off-ramp/convert-eur-to-token.md): Get the token amount required to reach a target EUR value — step 3 of the off-ramp flow. - [topup - SDK - BRRR Developer Docs](https://docs.brrr.network/sdk/references/off-ramp/topup.md): Execute an off-ramp by sending tokens from a user's wallet to a $holytag — the final step of the off-ramp flow. - [topupSelf - SDK - BRRR Developer Docs](https://docs.brrr.network/sdk/references/off-ramp/topup-self.md): Execute an off-ramp to the connected wallet's own Holyheld card — no $holytag required. ##### On-ramp - [convertTokenToEUR (On-Ramp) - SDK - BRRR Developer Docs](https://docs.brrr.network/sdk/references/on-ramp/convert-token-to-eur.md): Estimate the EUR value of a token amount before initiating an on-ramp — optional step in the on-ramp flow. - [convertEURToToken (On-Ramp) - SDK - BRRR Developer Docs](https://docs.brrr.network/sdk/references/on-ramp/convert-eur-to-token.md): Calculate the token amount equivalent to a given EUR input — optional step in the on-ramp flow. - [getOnRampEstimation - SDK - BRRR Developer Docs](https://docs.brrr.network/sdk/references/on-ramp/get-on-ramp-estimation.md): Estimate the network fee and final token amount for an on-ramp before submitting the request — optional but recommended. - [requestOnRamp - SDK - BRRR Developer Docs](https://docs.brrr.network/sdk/references/on-ramp/request-on-ramp.md): Submit an on-ramp request that the user then confirms in their Holyheld app — the primary execution step of the on-ramp flow. - [watchRequestId - SDK - BRRR Developer Docs](https://docs.brrr.network/sdk/references/on-ramp/watch-request-id.md): Poll for the outcome of a pending on-ramp request — resolves when the user approves, declines, or the timeout expires. ##### Common - [getServerSettings - SDK - BRRR Developer Docs](https://docs.brrr.network/sdk/references/common/get-server-settings.md): Fetch current SDK availability flags and EUR amount limits — call this before any off-ramp or on-ramp to confirm the service is live. - [validateAddress - SDK - BRRR Developer Docs](https://docs.brrr.network/sdk/references/common/validate-address.md): Check whether a wallet address is eligible for off-ramp (topupSelf) or on-ramp — call this before submitting a transaction. - [getTagInfo - SDK - BRRR Developer Docs](https://docs.brrr.network/sdk/references/common/get-tag-info.md): Look up a $holytag to verify it exists and is active before sending tokens to it in the off-ramp flow. - [getWalletBalances - SDK - BRRR Developer Docs](https://docs.brrr.network/sdk/references/common/get-wallet-balances.md): Retrieve all token balances held by a wallet address — useful for building a token selector UI before an off-ramp.