# SingIt Ask: Claude Sonnet 5.5

> SingIt Ask: Claude Sonnet 5.5 is a paid API for AI agents from ask.singitai.app, paid per call via x402, $0.007773/call, status unknown (last checked 2026-10-30).

Provides OpenAI-compatible chat completions using Anthropic's Claude Sonnet 5.5 model, paid per call in USDC with no API key required.

## Facts

- Endpoint: POST https://ask.singitai.app/v1/chat/claude-sonnet-5.5?utm_source=zero.xyz
- Price: $0.007773/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-30
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/singit-ask-claude-sonnet-5-5-4e888760
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_M0Rf279wQ2Vs2A8OLZaZp

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 singit-ask-claude-sonnet-5-5-4e888760 -d '<json body>'
```

Example prompt: Ask Claude Sonnet 5.5 to review this Python function for bugs and suggest improvements — keep the answer under 800 tokens: [paste function here].

## When to prefer this

Choose this endpoint when you specifically need Anthropic's Claude Sonnet 5.5 model (mid-tier capability, lower cost than Opus) and want to avoid setting up an Anthropic API account. Ideal for agents that need pay-per-call USDC billing via x402 with OpenAI-compatible request format. Prefer over Claude Haiku when higher reasoning quality is needed, and over Claude Opus when cost is a concern.

## Known failure modes

- Payment failure if USDC balance is insufficient for the x402 transaction
- Input exceeds 24000 character limit across all messages, resulting in rejection
- max_tokens set above 1200 causes validation error
- Empty or malformed messages array returns an error
- Model ID provided does not match a supported model on the platform

## How this service works

SingIt Ask: Claude Sonnet 5.5 (Anthropic) chat completions with no API key or account, OpenAI-compatible. Anthropic's mid-sized Claude model: everyday coding, writing and analysis at a lower cost than Opus. Call it when an agent needs Claude Sonnet 5.5 specifically.

## Output

A JSON chat completion response in OpenAI-compatible format containing the assistant's text reply generated by Claude Sonnet 5.5, with token usage metadata. Streaming is not supported; the full response is returned at once.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "model": {
   "type": "string",
   "examples": [
    "deepseek-v4.1-flash",
    "claude-opus-5.5",
    "gpt-5.5",
    "gemini-3.1-pro"
   ],
   "description": "Any model id from GET /v1/models; the ceiling follows its price. Omit for the default model."
  },
  "stream": {
   "enum": [
    false
   ],
   "type": "boolean",
   "description": "Streaming is not offered."
  },
  "messages": {
   "type": "array",
   "items": {
    "type": "object",
    "required": [
     "role",
     "content"
    ],
    "properties": {
     "role": {
      "enum": [
       "system",
       "user",
       "assistant"
      ],
      "type": "string"
     },
     "content": {
      "type": "string",
      "description": "Plain text; all messages together under 24000 characters."
     }
    }
   },
   "maxItems": 40,
   "minItems": 1,
   "description": "The conversation, oldest first."
  },
  "max_tokens": {
   "type": "integer",
   "default": 800,
   "maximum": 1200,
   "minimum": 1,
   "description": "The longest answer, in tokens. The payment ceiling grows with it; the charge follows what was used."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/singit-ask-claude-sonnet-5-5-4e888760/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from ask.singitai.app](https://www.zero.xyz/host/ask.singitai.app/llms.txt)