# X402-NVIDIA StepFun Step-3.5 Flash via Micropayment

> X402-NVIDIA StepFun Step-3.5 Flash via Micropayment is a paid API for AI agents from x402-nvidia.vercel.app, paid per call via x402, $0.105734/call, status unknown (last checked 2026-09-14).

Run StepFun Step-3.5 Flash chat completions via NVIDIA NIM with per-call USDC micropayment using the x402 protocol

## Facts

- Endpoint: POST https://x402-nvidia.vercel.app/api/stepfun-step-3-5-flash
- Price: $0.105734/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-nvidia-stepfun-step-3-5-flash-via-micropayment-64dbcab5
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_2zZxkTLtQ-P1N93t2kZ_l

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability x402-nvidia-stepfun-step-3-5-flash-via-micropayment-64dbcab5 -d '<json body>'
```

Example prompt: Using NVIDIA NIM's StepFun Step-3.5 Flash model, send this message and get a response: 'Explain the difference between supervised and unsupervised learning in two sentences.' — charge the $0.11 USDC per-call fee automatically.

## When to prefer this

Choose this endpoint when you need access to StepFun Step-3.5 Flash specifically via NVIDIA NIM and want to pay per call in USDC without managing a long-term API subscription or API key — ideal for agents that need on-demand, pay-as-you-go LLM inference with crypto-native payment settlement.

## Known failure modes

- Payment not attached or insufficient USDC balance — 402 Payment Required returned
- Invalid or malformed message format — 400 Bad Request
- Model temporarily unavailable on NVIDIA NIM — 503 Service Unavailable
- x402 facilitator unreachable — payment cannot be processed
- Request exceeds model context window — truncation or error response

## How this service works

Access 48+ NVIDIA NIM AI models via x402 micropayments. Chat completions, vision, safety, translation, and more.

## Output

A chat completion response object containing a choices array with the assistant's generated message content, role, and any finish reason returned by the StepFun Step-3.5 Flash model hosted on NVIDIA NIM.

## Response schema (JSON Schema)

```json
{
 "type": "object",
 "example": {
  "choices": [
   {
    "message": {
     "role": "assistant",
     "content": "Hello!"
    }
   }
  ]
 },
 "properties": {
  "choices": {
   "type": "array",
   "description": "Model responses"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-nvidia-stepfun-step-3-5-flash-via-micropayment-64dbcab5/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402-nvidia.vercel.app](https://www.zero.xyz/host/x402-nvidia.vercel.app/llms.txt)