How much does a image-probe call cost?

$0.003 per call, paid in USDC on Base via x402, with no account and no API key.

What does image-probe return?

A JSON object with 8 top-level fields: source_url, format, width, height, channels, space, has_alpha and bytes. The example on this page is a real call over images/tiles-64x40.png.

What happens when a image-probe call fails?

The tool answers with a typed JSON error from the errors table. Payment is settled only after the tool has produced its result; a call that fails inside the tool is never settled. A 503 upstream_unavailable can follow a settled call; the x402 payments guide covers it, 429, 402 and an uncertain 500.

catalogue / tools / Images / Image Probe API

Image Probe API

Reports an image's format and pixel dimensions from its header, without decoding the pixels.

Endpoint: POST /v1/image-probe
Price: $0.003 per call
Family: Images
Docs: /docs/image-probe

01When to use it

Reading an image header safely needs a real decoder and a hardened fetch: an agent that pulls the URL itself walks past every SSRF control, and carrying an image library per call is not something an agent does inline.

When not to use it

The input is over 25 MB (26,214,400 bytes): image-probe answers too_large (413).
The destination needs more than 20 s to answer: the call ends with upstream_timeout (424).
The destination is on a private or local network: the network guard refuses it with blocked_target (403).

02Parameters

Field	Type	Required	Description
url	string	yes	Absolute http(s) URL of the image, up to 2048 characters; redirects are followed, the bytes must be jpeg, png, gif, webp, tiff, avif, heic or svg by signature, and only the header is parsed.

03Limits

Limit	Value
Size cap	25 MB (26,214,400 bytes)
Timeout	20 s

04Example

The published example of image-probe, verbatim: the request body and the response it returns.

Request

POST /v1/image-probe
content-type: application/json
payment-signature: <base64 x402 payload>

{
  "url": "https://grist.tools/samples/images/tiles-64x40.png"
}

Response

200 OK
payment-response: <base64 settlement receipt>

{
  "source_url": "https://grist.tools/samples/images/tiles-64x40.png",
  "format": "png",
  "width": 64,
  "height": 40,
  "channels": 4,
  "space": "srgb",
  "has_alpha": true,
  "bytes": 10348
}

Sample file: images/tiles-64x40.png. 64x40 RGBA PNG test card: four flat colour tiles inside a transparent 8-pixel border, written with uncompressed deflate blocks.

In the sample itself: its IHDR chunk declares 64 by 40 pixels, 8-bit truecolour RGB with alpha and no interlacing. The chunks run IHDR, IDAT and IEND.

Response field	Type	In the example
source_url	string	"https://grist.tools/samples/images/tiles-64x40.png"
format	string	"png"
width	number	64
height	number	40
channels	number	4
space	string	"srgb"
has_alpha	boolean	true
bytes	number	10348

05Call it from code

JavaScript

// image-probe: $0.003 per call, paid in USD Coin on eip155:8453 via x402
// Install: npm install @x402/fetch@2 @x402/evm@2 viem@2
// Save as client.mjs (ES module, Node 18+), export EVM_PRIVATE_KEY with the paying wallet's key in your shell, then run: node client.mjs
// The wrapper reads the 402 (payment-required), signs and retries with payment-signature.
import { wrapFetchWithPayment, x402Client, decodePaymentResponseHeader } from '@x402/fetch'
import { ExactEvmScheme } from '@x402/evm/exact/client'
import { privateKeyToAccount } from 'viem/accounts'

const account = privateKeyToAccount(process.env.EVM_PRIVATE_KEY)
const client = new x402Client().register('eip155:8453', new ExactEvmScheme(account))
const fetchWithPayment = wrapFetchWithPayment(fetch, client)

const body = {
  "url": "https://grist.tools/samples/images/tiles-64x40.png"
}

const res = await fetchWithPayment('https://grist.tools/v1/image-probe', {
  method: 'POST',
  headers: { 'content-type': 'application/json' },
  body: JSON.stringify(body),
})
console.log(res.status, await res.json())
const settle = res.headers.get('payment-response')
if (settle) console.log(decodePaymentResponseHeader(settle).transaction)

Python

# image-probe: $0.003 per call, paid in USD Coin on eip155:8453 via x402
# Install: pip install "x402[requests,evm]>=2.24,<3"
# The session reads the 402 (payment-required), signs and retries with payment-signature.
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http import decode_payment_response_header
from x402.http.clients.requests import x402_requests
from x402.mechanisms.evm.exact import register_exact_evm_client
from x402.mechanisms.evm.signers import EthAccountSigner

account = Account.from_key(os.environ["EVM_PRIVATE_KEY"])
client = x402ClientSync()
register_exact_evm_client(client, EthAccountSigner(account), networks="eip155:8453")
session = x402_requests(client)

payload = {
    "url": "https://grist.tools/samples/images/tiles-64x40.png"
}

res = session.post("https://grist.tools/v1/image-probe", json=payload)
print(res.status_code, res.json())
settle = res.headers.get("payment-response")
if settle:
    print(decode_payment_response_header(settle).transaction)

curl

# image-probe: $0.003 per call, paid in USD Coin on eip155:8453 via x402
# 1. Unpaid call: HTTP 402, the requirements in the payment-required header (base64 JSON) and in the body.
curl -i -X POST 'https://grist.tools/v1/image-probe' -H 'content-type: application/json' -d '{"url":"https://grist.tools/samples/images/tiles-64x40.png"}'

# 2. Same call with the signed payment (an EIP-3009 authorization, EIP-712 signed: it cannot be
#    typed by hand). x-payment is accepted as the v1 alternative. HTTP 200 carries payment-response.
curl -i -X POST 'https://grist.tools/v1/image-probe' -H 'content-type: application/json' -H 'payment-signature: <base64 x402 payload>' -d '{"url":"https://grist.tools/samples/images/tiles-64x40.png"}'

06Errors

Code	HTTP	For this service
invalid_input	400	The body does not match the schema; its fields are url.
blocked_target	403
unreachable_target	424
upstream_timeout	424
unsupported_content_type	415
too_large	413
unprocessable	422
internal	500

Input that is rejected before the tool runs (malformed JSON, schema mismatch, body over the size limit) is never charged.

When each code is raised, and what it means for payment: /docs/image-probe.

07Questions

How much does a image-probe call cost?: $0.003 per call, paid in USDC on Base via x402, with no account and no API key.
What does image-probe return?: A JSON object with 8 top-level fields: source_url, format, width, height, channels, space, has_alpha and bytes. The example on this page is a real call over images/tiles-64x40.png.
What happens when a image-probe call fails?: The tool answers with a typed JSON error from the errors table. Payment is settled only after the tool has produced its result; a call that fails inside the tool is never settled. A 503 upstream_unavailable can follow a settled call; the x402 payments guide covers it, 429, 402 and an uncertain 500.