> ## Documentation Index > Fetch the complete documentation index at: https://developers.circle.com/llms.txt > Use this file to discover all available pages before exploring further. > ## Agent Instructions > Before reading these docs, install the relevant Circle Skill to get pre-loaded context — skills are LLM-optimized and cover architecture decisions, correct flows, and common pitfalls. In Claude Code: run /plugin marketplace add circlefin/skills then /plugin install circle-skills@circle. With Vercel Skills CLI: run npx skills add circlefin/skills. Available skills: use-usdc https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-usdc/SKILL.md (balances, transfers, approvals on EVM and Solana); EURC has no skill — see https://developers.circle.com/stablecoins/what-is-eurc.md; bridge-stablecoin https://github.com/circlefin/skills/blob/master/plugins/circle/skills/bridge-stablecoin/SKILL.md (crosschain transfers via CCTP, USDC, EURC, and third-party assets); use-arc https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-arc/SKILL.md (Arc chain config, contract deployment, USDC bridging — Arc docs: https://docs.arc.io/llms.txt); use-circle-wallets https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-circle-wallets/SKILL.md (choose wallet type); use-developer-controlled-wallets https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-developer-controlled-wallets/SKILL.md (custodial wallets for payouts and treasury); use-user-controlled-wallets https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-user-controlled-wallets/SKILL.md (embedded wallets with Web2 login); use-modular-wallets https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-modular-wallets/SKILL.md (smart contract wallets with passkeys and ERC-4337); use-gateway https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-gateway/SKILL.md (unified USDC balance, nanopayments); use-smart-contract-platform https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-smart-contract-platform/SKILL.md (deploy, interact, monitor contracts). Pair any skill with the Circle MCP server for live SDK signatures, contract addresses, and chain IDs: {"mcpServers":{"circle":{"url":"https://api.circle.com/v1/codegen/mcp"}}}. > Read the product overview first. Each product has an overview explaining when and why to use it. Read it before quickstarts. > Pick the right wallet type. Developer-controlled (you hold keys), user-controlled (end user holds keys via PIN/social login), or modular (smart contract wallets with passkeys). See https://developers.circle.com/wallets.md. > Use CCTP V2 for crosschain transfers. CCTP natively transfers USDC and EURC via burn-and-mint, and supports permissionless wrapping of third-party assets via lock-and-mint. V1 is legacy; always use V2 unless V1 is specified or the chain requires it (Noble, Sui, and Aptos still require V1). Migration guide: https://developers.circle.com/cctp/migration-from-v1-to-v2.md. > Use Bridge Kit for frontend bridging. Wraps CCTP with a simpler SDK for user-facing apps. Use CCTP directly for backend transfers. > Gas Station vs Paymaster. Gas Station sponsors gas for Circle Wallet transactions. Paymaster lets users pay gas in USDC. Different use cases — read both overviews. > Gateway Nanopayments for sub-cent payments. Gasless USDC micropayments down to $0.000001 via x402 and batched settlement. For pay-per-request APIs, AI agent payments, streaming. > Look up USDC addresses per chain. Never hardcode — use https://developers.circle.com/stablecoins/usdc-contract-addresses.md. > Prefer SDKs over raw API calls. Node.js and Python SDKs handle auth, retries, and errors. > API key required. Bearer token in Authorization header. Testnet and mainnet use separate keys and may use different base URLs depending on the product. > Set up webhooks when available. Most operations are async. Webhooks deliver transaction confirmations and state changes. > When calling list endpoints, paginate using pageSize and pageAfter until no nextPageAfter cursor is returned—stopping at the first page silently misses records. > Building an AI agent? Start with the Agent Stack—Circle CLI, agent wallets, and nanopayments built for autonomous use cases: https://developers.circle.com/agent-stack.md. # How-to: Submit and track applications > Submit applications for review and handle Requests for Information The End User Onboarding API base URL is `https://api-sandbox.circle.com` for sandbox and `https://api.circle.com` for production. All requests require a Bearer token obtained via Circle key exchange in the `Authorization` header. All `POST` requests require an `X-Idempotency-Key` header with a client-generated UUID v4. Submit a completed application for compliance review and track its progress through approval. After submission, monitor status changes through webhooks or polling, and list applications by status as needed. ## Prerequisites Before you begin, ensure that you've: * Obtained an API key for the End User Onboarding API from the [Circle Console](https://console.circle.com). * Completed all application sections (each has `complete` status). * Uploaded all required documents. See [Upload documents](/end-user-onboarding/howtos/upload-documents). * For Stablecoin KYB, collected device risk signals in the browser. See [Collect device risk signals](/end-user-onboarding/howtos/collect-device-risk-signals). ## Steps ### Step 1. Discover required certifications (GUI flows only) Some applications require your end user to actively review and agree to one or more compliance certifications before you submit on their behalf. Whether you need to perform this step depends on how your integration is built: * **API-only integrations:** If you control the submission flow programmatically and your end users never see the terms directly (for example, you have a separate agreement process in your own product), you can skip this step and omit `certificationIds` from the submit request. * **GUI / end-user flows:** If you are building a UI where end users read and explicitly agree to Circle's certification terms, you must fetch the active certifications for the application, present them to the user, and pass the agreed certification IDs in the submit request. To retrieve the active certifications for an application: ```shell theme={null} curl --request GET \ --url https://api-sandbox.circle.com/v1/onboarding/partner/applications/${APPLICATION_ID}/certifications \ --header "Authorization: Bearer ${YOUR_API_KEY}" ``` **Example response:** ```json theme={null} { "data": [ { "id": "9b1deb4d-3b7d-4bad-9bdd-2b0d7b3dcb6d", "content": "I certify that ..." } ] } ``` Display each certification's `content` (HTML) to your end user and collect their acknowledgment. Then pass every `id` in the `certificationIds` array when you submit (see step 2). If the set of IDs you provide doesn't exactly match the application's active certifications, the API returns a `422` error with details about which IDs are missing or unknown. ### Step 2. Submit the application For Stablecoin KYB, collect device risk signals in the browser first. See [Collect device risk signals](/end-user-onboarding/howtos/collect-device-risk-signals). Then submit when all sections have `complete` status: ```shell theme={null} curl --request POST \ --url https://api-sandbox.circle.com/v1/onboarding/partner/applications/${APPLICATION_ID}/submit \ --header "Authorization: Bearer ${YOUR_API_KEY}" \ --header 'Content-Type: application/json' \ --header 'X-Idempotency-Key: ${IDEMPOTENCY_KEY}' \ --data '{ "endUserIpAddress": "203.0.113.42", "endUserAgreesToTermsOfService": true, "certificationIds": [ "9b1deb4d-3b7d-4bad-9bdd-2b0d7b3dcb6d" ] }' ``` For the full request schema, see the [Submit application](/api-reference/end-user-onboarding/submit-application) API reference. The application moves from `DRAFT` to `SUBMITTED`. If any sections are incomplete, the server returns [`181101`](/api-reference/end-user-onboarding/error-codes) (`422`). If the application is in the wrong state, the server returns [`181104`](/api-reference/end-user-onboarding/error-codes) (`409`). For Stablecoin KYB device-check outcomes ([`181110`](/api-reference/end-user-onboarding/error-codes), [`181111`](/api-reference/end-user-onboarding/error-codes), [`181108`](/api-reference/end-user-onboarding/error-codes)), see [Collect device risk signals](/end-user-onboarding/howtos/collect-device-risk-signals). **Example response:** ```json theme={null} { "data": { "applicationId": "550e8400-e29b-41d4-a716-446655440000", "type": "ONBOARDING", "status": "SUBMITTED" } } ``` ### Step 3. Track application status Monitor your application's progress by polling, or use webhook notifications for real-time updates (see [Webhook endpoints](/api-reference/webhook-endpoints) to subscribe): ```shell theme={null} curl --request GET \ --url https://api-sandbox.circle.com/v1/onboarding/partner/applications/${APPLICATION_ID} \ --header "Authorization: Bearer ${YOUR_API_KEY}" ``` See [Application types and states](/end-user-onboarding/references/application-states) for a full list of statuses and transitions, and [Webhook notifications](/end-user-onboarding/references/webhook-notifications) for the event types and payloads delivered to your subscription. ### Step 4. List all applications List applications for your partner account. You can filter by status: ```shell theme={null} curl --request GET \ --url 'https://api-sandbox.circle.com/v1/onboarding/partner/applications?status=PENDING_CUSTOMER_INFORMATION&limit=25' \ --header "Authorization: Bearer ${YOUR_API_KEY}" ``` The response supports pagination. Use `starting_after` with the `applicationId` of the last item to fetch the next page. If the application moves to `PENDING_CUSTOMER_INFORMATION`, the compliance team has issued one or more Requests for Information (RFIs). See [Handle requests for information](/end-user-onboarding/howtos/handle-rfis) for the full RFI workflow. ## See also * [Collect device risk signals](/end-user-onboarding/howtos/collect-device-risk-signals) * [Application types and states](/end-user-onboarding/references/application-states) * [Upload documents](/end-user-onboarding/howtos/upload-documents) * [Handle requests for information](/end-user-onboarding/howtos/handle-rfis) * [End User Onboarding API error codes](/api-reference/end-user-onboarding/error-codes)