> ## 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.

# Integrate with JSON Schema

To facilitate the effective passing of RFI data, CPN provides
[JSON Schema](/cpn/concepts/api/json-schema) that gives a clear,
machine-readable contract you can validate your response against. This guide
provides information about how to integrate with the JSON Schema returned by the
[get details for an RFI endpoint](/api-reference/cpn/cpn-platform/get-rfi).

## Steps

Use the following steps to retrieve JSON Schema for a given quote and respond
with the required information.

### Step 1: Get the JSON Schema

Call the [get details for an RFI](/api-reference/cpn/cpn-platform/get-rfi)
endpoint. The API returns a JSON Schema object that defines the fields that must
be transmitted in the RFI response.

### Step 2: Build a JSON response

Using the schema as a blueprint, construct your RFI data as a JSON object. For
example, if the schema requires the `address` field, you should create a nested
JSON object for the address, as defined by the `properties` and `$defs` in the
schema.

### Step 3: Validate the response

Before encrypting the response for transit, CPN expects that you perform
client-side validation on the data. Using a JSON Schema validation library,
check your constructed JSON objects against the schemas from Step 1. This should
catch any structural or formatting errors before you interact with the CPN API.

### Step 4: Encrypt the response

Once validated, convert your JSON objects to strings and encrypt them. The steps
outlined in
[How-to: Encrypt Travel Rule and Beneficiary Account Data](/cpn/guides/payments/encrypt-travel-rule-beneficiary-data)
also apply to encrypting RFI data for transit.

### Step 5: Transmit the payload

Send the encrypted payload to the
[submit RFI data endpoint](/api-reference/cpn/cpn-platform/submit-rfi).

The following is an example payload:

```json JSON theme={null}
{
  "rfi": {
    "version": 1,
    "data": "eyJhbGciOiJFQ0RILUVTK0ExMjhLVyIsImVuYyI6IkExMjhHQ00iLCJlcGsiOnsiY3J2IjoiUC0yNTYiLCJrdHkiOiJFQyIsIngiOiI1TEtTbUtsNmVYV0dQNHlGb2tVaks4RGppU0l5YWpQdzJ6UUp1YVhFbEZzIiwieSI6IlRVT29MTV8wc294b0UzYVFmSExlUzRlRkZ3RU9tZ1VDRUh1eDVRMXdVYTQifX0.kVGnfB8eIqxq3bMvhedxUmZvkCrRfQOy.bTUOc_ilvZjb9VYP.pOS6Ul8Jnp_pijWtaQYC0b1NLN1Nc-t_MTsfj5EZy6s62ijQWGtAoo3enwx3gOpXIQDIIF7c-F3KSrVO33a5RIF8a4tvU7pRk_JDKVgHFVpSzvOaUHNHsMUvvctAncx1SneVE_gnm5ATkWO4_1i7irTkb-cjWLmvJ1vVEyJiC9ZgsEdK_eBAewpZTyyKxvoxBpo8IZ3g7qax712TvMsNpIJ_faQmsyRKwt2kBxDPyrWILcIvS1qij6uVOsEP2R6LXbWfBqVbklsgNPWjndXSmOJmsTdBjFzublMLSHmLxkfaD9gt3DxgD16rqDlKO9KmaRF3r322VumP4hrlfOsZUHHcVGeTpgjZwI9jrj76PiYtyCOeR7-kz97PamqrOQAfWRE8Rcp8QdCO6yFHFe3N2pI5kWakH783DVDAsm_x2VY_V8vCDe-xkIoJOabx3LqaxHq8_x_ATXZ01NX-5F9VqgtE73FOIGhinxt8G-Kfxvdlx6gv-QSfBvigVuoR1OCSPNB3OHirEKXY3IjWnjZuENNnXl9CqrCsHQZS1eb1KcaIkg_2NF6gi54htX6ijpUtyXS03IGZW6Bn6CSWqmmvMStIAIYO-8ZJrrleeCfU6WY5KjFlIvN6th-tE41JNJWS9mVqhjzwPC7GQ5bGkqq2zJKhALOuN_0oG4jXOYo1s3YAn-xw3kpq46fYyUrX4nLSocaKDeKOMMqh57_jcMDmHrXdmjlHGPMrBPdU_deub121c3ofTKgJg4KRC8mcTYcXe71uflARAr24msd9A_IPPVbhfvs06HOVKL2-jK6r_WL_9vWU3q-OPQHU3eWUOhI18vZ0CkGqJjtEKyBBmc4inWEbrsO02P2Zd5VTBCIoAaNrpY6n5mNyKPo6-PyrxNy27d6u2yoZvjG6QSuUO9DaX4AyGsE87agh_XgLW9RPXfcZQ7F5aUCQwEA0cF9YSEaYYBGziS7oQ99D1th1MQqEPcFxD5YPdyaPykU3Zbf5T8HSZz1risMbgQu97eXoarxm801pdw5cuKijqj39BVrgdLUfaQ9P-iGWcVJk8ZVXfHK3JHGaBuIjYNIy5lHF3TsKgV2x-wWxqER9vPdgejAGirkxHQaKPt2rg0rmbk3R7YTibT7yTKwO1PRiewi0lxKWvZqDbCoedyuYZCR0vup4S1ZVYX6uGBn-F5ODrnLoAZTbnV1tjDJgxFpA8EKsXWTrc78XH0715lY2OnbDtBOLMbxFJjK1_YDRU2UMkZTEx5BrhR4YibBd4-BCZT-dWTxanOHMxTKl823tyggY5lBQ8DlsLj1qZpOxKWYTM8WrLCZa7vZo9FmXw38FxYrqbwespe7xdS7onfmlI4Ug92eTtZ31FbZfcqOiAGgH9Etkj1M9scP0is6zVC6cIUQzC3NmHNxNtPv6XjMUWigijosvs7x9-qyVCqzJZlEGck2BJ6Uk7ug9QKcxHtaWgtuHPnA77KVE3Vi_dikYaXzxIdgjrGtqqUhXEhrAFkesvJ0UeH1ac94e-R8UrJX75w4DDoRyaFxQhDFdHVtD0ceVN7ekYJkmoS2eSAzWDwsKUvUrmafcfpQ922tZGq0RvnMh39SWy6I6xRFyYHarra24Gbawa5_THjB8TkHJ180giPC3KQAa_6Vz8CP-fks6_-MdGXPW0SYhNghNi_14ZXQ3rZYHaTICgeHhBfhJ4MQ6OlRkiRCrIkM5WSOTS_H715aeyUCL-dlZ0TiG2DpAIXkN1KMRp0jL_W12pg5SjKFAlOGnQgkgj9rO_C7pLxMyIhgEUKPHXMGN6Q7tpVhAAyTl0tabd7cvyWnf5L4UiyIpvb1qrt1bY6-VNA4KXz6Y5uiiBYFF_FIN3K6YZCT4l0zuh_gxmP9eba7zM5kgas1tr1IxYWI-mQiE9Rb8rX0hqXpMj27h9Mf_Sn56TJeEmW8d8x2Xy2Nb7KU9vQO-6uc_taXP0Lv5LFcSwZkdVe7FOeZD-GoaNDly9MdhXI4ELP4MOZXZFJeN7aCJvJeLRBPWnoM2aazDwtlA_KfhZVFtCsKKjJazv6J9h6CDHAm7NuexVJiPdtS1yknQDWrIBfneaLJasmtuhuAbRPtiTvvhQOXt51q0G7sjCSmmeNMwb5fFphe4wLJNmsbdgMFDcUVzb0ImIArCxqBEEK8uuRGcYaRifaLv0zkk29NAT99Ux580zaeN_x7aIMpJTt7jLP0-HZ-QU3MAGg3PLJ3_Oly6ABoULkEkmRhF0TtpU8z-kmmN6FtmzZK74kYEC75smgVTnnJK1kBdsZw9cxHeUx8aDJGrS3OK-uYN0dPJls2LC7X1rHD7ES179nPVBeJA2REm-jSlhVlV_I7JrVzlcXs0Fhx0hX-OgMKz_yQNHnM6RbgGnSLDcvND7vXqkEMgHeDRomhU1hMeu0DymctTKawtzIkV7MYwoibLDUeMvaXN8MicMs64D8I3Ld7BLtFf9o8rMeeNJ0Om7xdl9SGD2RYAep0cxw2rEIIr859e1vutBuvrrMz09dZKd05t1lu0jRztkQzUW9N-VZh9muTAoh_s3NrF2ZTFnRAfzxohwNLxxmX-Ov94FXBhuRHBQXb931I5m2URglrYcoAZ8RFoiAWW2AkHcyb5PRoQIt-LQhOM-bcn1VB44Okh10jqWpGbLno6AvE5FcoRVcspb0tor9EbksW2cipoypcaat5NhQgvo2rAPmkHGi8iB-z_xWORvUkaA2xknNW59myO6qTvjYQ_1P1ESbRO30nUeqgP3VoZrC1-bi9IbgSi-na31xEhdr-ZGuvtRSzyhWwqfviJgSMZ6_kkGW3gUI4ldurTwss6gDHWYmdV-lHtPMfYuD2KMQk1EyJ-3vZx0syLKDACL37HqAYvkW5GiOxrK9cNrSInQ8rZMDkXsaCZMEtvs03Qw2DyCBdoFeXPvFHJ6Vetou-7Oo6rdlmSkt5KdA-w9KKVIAt9WtYxNc-wjFm-vOMcOHb_xxzacDzYFJj8NxdW8GaVdrCvh3j5Yakr_3vSvRM5rpzQKMqw-B53SWV3oOHYu29qso5zSTz-dvAlZUL8Z1a3s13qdwhUkkRexIi6oTU0Da21pT-gCan2jSY_VKR8JdirKTLocn74JZ3InF8iH8XhOD0X7ySIbB69HqMLYRd9r13q2odfJ3cN1CWSF71zgIuZoYSbkO9DeFvCImA-WEIWrP1kJiYlpJi8VnFNQs8XWIxdCydft-8zvoXZbi0MoNt3kJExbKx7dReHx6B-6iwjuW8-o5RbeMvdTIYTp-y6YPsFhcVCvTlS7IefXqG4G3OrnNc5JIVnvdYXWCWUdWguiKdqB6FL_LSWOtsWrB6nIv69WP1WJJSa0Oa_EkxEwXK1BGH9-QpMqkP6rATSvsbaTywfCxqUqm7SzYH81lSCIvI5J7bWX5blk9rNZbp3aSeEpVRm03vwLrgUHLv9vMAopNnw5fZGKfcg3I5ZWYHNQo5BZk9LVpebMBYGijwNDnuFu08eF7ShlEzy50NsvgeDxZtfUVx8cviYn0MoTJBPlz1mXRSIr3zDIpefxDGnsQ1KK8LTi0Gbnt_ybeiT4yTmajrPLE4566D6AQIdDmCg_RsBtB_lAw.S2qu0MNMu2WNiEYoHh25ww"
  }
}
```