Claude Sonnet API
Claude Sonnet API - pay per call, no API key. OpenAI-format chat completions on anthropic/claude-sonnet-5.5, pinned to Anthropic's own OpenRouter endpoint for reliability. You sign a fixed price computed from your max_tokens; unused tokens are not refunded. 20s server-side timeout - never charged if it fires; set your client timeout to 30s. Try GET /llm/claude-sonnet/sample.
Answeringour last check, 2026-09-30
1 of 1checks answered this week
902 msmedian answer time
$0.001892listed price per call
$0.001892price it asked us
Paid test badge: not yet. The checks above are free: we call the tool without paying and read the payment request it sends back. The Verified badge needs paid calls whose answers match the promised output, and nobody can buy a badge.
Endpoint
POST https://x402.agentindex.world/llm/claude-sonnet
| Category | Market data |
|---|---|
| Provider host | x402.agentindex.world |
| Networks | eip155:8453 |
| Payment schemes | exact |
| Self-reported calls, 30 days | 0 from 0 payers (the provider's figure, not ours) |
Our checks, last 30 days
| Day | Result | HTTP | Asked | Time |
|---|---|---|---|---|
| 2026-09-30 | valid payment request | 402 | $0.001892 | 902 ms |
Example input (from the provider)
{
"body": {
"max_tokens": 150,
"messages": [
{
"content": "Summarize in one sentence: The Eiffel Tower is a wrought-iron lattice tower on the Champ de Mars in Paris, France. It was designed by Gustave Eiffel's engineering company and built as the entrance arch for the 1889 World's Fair. Initially criticized by some of France's leading artists and intellectuals for its design, it has become a global cultural icon of France and one of the most recognizable structures in the world, attracting millions of visitors every year.",
"role": "user"
}
]
},
"bodyType": "json",
"method": "POST",
"type": "http"
}
Promised output schema (from the provider)
{
"$schema": "https://json-schema.org/draft/2020-12/schema",
"properties": {
"input": {
"additionalProperties": false,
"properties": {
"body": {
"properties": {
"max_tokens": {
"description": "Max completion tokens, capped at 4096 - also bounds the price ceiling.",
"type": "integer"
},
"messages": {
"description": "OpenAI-format chat messages: [{role, content}, ...].",
"items": {
"type": "object"
},
"minItems": 1,
"type": "array"
}
},
"required": [
"messages"
]
},
"bodyType": {
"enum": [
"json",
"form-data",
"text"
],
"type": "string"
},
"method": {
"enum": [
"POST",
"PUT",
"PATCH"
],
"type": "string"
},
"type": {
"const": "http",
"type": "string"
}
},
"required": [
"type",
"method",
"bodyType",
"body"
],
"type": "object"
},
"output": {
"properties": {
"example": {
"properties": {
"choices": {
"items": {
"type": "object"
},
"type": "array"
},
"id": {
"type": "string"
},
"model": {
"type": "string"
},
"usage": {
"type": "object"
},
"x402_receipt": {
"type": "object"
}
},
"required": [
"choices",
"usage"
],
"type": "object"
},
"type": {
"type": "string"
}
},
"required": [
"type"
],
"type": "object"
}
},
"required": [
"input"
],
"type": "object"
}