x402 is an HTTP payment protocol. An unpaid request returns HTTP 402 with a payment offer; sign one offer and retry the same request with proof of payment.

Do I need an account?

No account or API key is needed for these x402 calls.

Base or Solana, paid in USDC. This page focuses on Base.

Google: Gemini 4 Carbon: pay per request with x402

Call Google: Gemini 4 Carbon with no account or API key. Pay per request in USDC on Base via x402. Price: $0.51142/1M input, $2.5571/1M output tokens.

Pay per request

Send a request to ask.singitai.app, get HTTP 402 with the exact price, pay in USDC on Base, get the answer. No signup, no monthly plan.

Modality: chat · Provider: Google · Context window: 1,048,576 tokens · Tags: vision, reasoning, audio

Price

USD per 1M tokens	Input	Output
SingIt price (expected)	$0.51142	$2.5571
List price of the model (for reference)	$2	$10

The expected price is based on what answers from this model have cost us. Sample size n = 1 of the last 20 paid answers. This is a preliminary sample, not yet a stable median. It is an expected price, not a guarantee; you pay what each answer actually used.

You pay the price shown for each model, metered by what the answer actually used, plus a settlement fee per request ($0.001 on Base, $0.002 on Solana).

Per request, reference request

One short message, max_tokens 800 (30 characters), 12 input tokens. upto settles actual usage, so a real answer normally costs less; exact is flat, with no refund.

Network	upto ceiling (USD)	exact flat price (USD)
Base	$0.003764	$0.002151
Solana	$0.004764	$0.003151

Prices as of 2026-11-10 12:03:14 UTC (snapshot of ask.singitai.app/v1/models and /pricing.json). Live: /v1/models and /pricing.json. Live values are authoritative and the 402 response states the exact price.

Call it with x402

curl -i -X POST https://ask.singitai.app/v1/chat/gemini-4-carbon \
  -H 'Content-Type: application/json' \
  -d '{"model":"gemini-4-carbon","max_tokens":400,"messages":[{"role":"user","content":"Say hello in one sentence."}]}'

The unpaid POST returns HTTP 402 and a PAYMENT-REQUIRED header: base64 JSON, x402 v2. Sign one offer (upto first, then exact; Base then Solana) and retry the same request with the PAYMENT-SIGNATURE header. HTTP 200 returns choices[0].message.content and billing.totalAtomic.

Follow the first paid call walkthrough, developer guide and llms.txt.

For a free try, choose from 6 free models, for example free/deepseek-v4.1-flash: 20 answers a day per network, no wallet. The shared daily cost cap is $0.25; free answers may run out for the day (free_budget_exhausted) and return at midnight UTC.

Use it from an agent

MCP: https://app.singitai.app/mcp. Free tools without a key: list_models, get_price, list_price_symbols.

The elizaOS plugin @singitai/plugin-singit has a paid-chat action that pays on Base. Its per-call and per-day caps are held in the plugin's memory: in-process, reset on restart, not on-chain, not enforced by SingIt's servers. It does not use AgentAllowance.

Give your agent a budget

Agent spending limits for USDC on Base · How to limit what an AI agent can spend · x402 payments with a budget for AI agents

Related models

All model pages

FAQ

What is x402?: x402 is an HTTP payment protocol. An unpaid request returns HTTP 402 with a payment offer; sign one offer and retry the same request with proof of payment.
Do I need an account?: No account or API key is needed for these x402 calls.
Which network? Base?: Base or Solana, paid in USDC. This page focuses on Base.