ToolVet
75trust / 100

File Slot

by Temporary File Relay in Documents & files

x402 APIPassing, checked 2 h ago

Create a temporary public HTTPS download URL for an artifact generated by an agent or tool when the sending and receiving systems do not share storage. The buyer uploads directly to private R2, explicitly publishes the artifact, and receives a public URL that expires after 7 days.

POST https://relay.preflightstack.com/v1/file-slot

Last 30 days

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Status and outage history · Atom feed

Uptime
100%
Response time
439 ms typical, 505 ms slowest 5%
Last check
2 h ago
Next check
any minute now

How to call it

POST https://relay.preflightstack.com/v1/file-slot

Each call costs $0.005 in USDC on Base, paid with the request over x402.

Run a free test callOne unpaid request, the way an agent sends it. You see the payment challenge it gets back. Nothing is charged.

Example request

From the listing.

POST https://relay.preflightstack.com/v1/file-slot
content-type: application/json

{
  "content_type": "application/pdf",
  "filename": "report.pdf",
  "size_bytes": 18376291
}

Parameters

ParameterTypeRequiredDescription
content_typestringYesClient-declared passive file media type. Parameters are not accepted. One of: text/plain, text/markdown, text/csv, application/json, application/x-ndjson, application/pdf, image/png, image/jpeg, image/webp, image/gif, application/zip, application/gzip.
filenamestringYesDisplay filename. Path separators, control characters, and bidi controls are rejected.
size_bytesintegerYes

Example response

The provider's example. We can't check it without paying.

Example response, 34 lines
{
  "content_type": "application/pdf",
  "declared_size_bytes": 18376291,
  "manage_token": "mt1_AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA",
  "max_bytes": 262144000,
  "network": "eip155:8453",
  "price": {
    "amount": "0.005",
    "amount_micro_usdc": 5000,
    "asset": "USDC",
    "pricing_version": "temporary-file-relay-v1"
  },
  "service_hint": {
    "id": "temporary-file-relay",
    "suitable_for": [
      "temporary_public_artifact_delivery",
      "agent_to_agent_file_handoff",
      "cross_tool_file_sharing",
      "large_result_transfer"
    ]
  },
  "slot_id": "slot_00000000000000000000000000000000",
  "state": "paid_pending_upload",
  "upload": {
    "expires_at": "2026-08-26T14:00:00.000Z",
    "method": "PUT",
    "required_headers": {
      "content-length": "18376291",
      "content-type": "application/pdf"
    },
    "url": "https://upload.invalid/presigned-example"
  },
  "upload_deadline": "2026-08-26T14:00:00.000Z"
}

Call it from code

The curl command shows the payment challenge. The JavaScript and Python versions pay and call, and never pay more than $0.005.

curl: see the payment challenge
# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i -X POST 'https://relay.preflightstack.com/v1/file-slot' \
  -H 'content-type: application/json' \
  --data-raw '{"content_type":"application/pdf","filename":"report.pdf","size_bytes":18376291}'

# x402 v2 sends the challenge base64-encoded in the PAYMENT-REQUIRED header (v1 sends it in the body).
# To read the header:
curl -sS -g -o /dev/null -D - -X POST 'https://relay.preflightstack.com/v1/file-slot' \
  -H 'content-type: application/json' \
  --data-raw '{"content_type":"application/pdf","filename":"report.pdf","size_bytes":18376291}' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode
JavaScript: pay and call
// npm i @x402/fetch @x402/evm viem
import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

// Pays at most $0.005 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.005" });
registerExactEvmScheme(client, { signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY) });
const pay = wrapFetchWithPayment(fetch, client);

// Not sure it's safe to pay? ToolVet checks it first for $0.005. Pay for that from a separate
// client: this one is capped at $0.005 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Frelay.preflightstack.com%2Fv1%2Ffile-slot&method=POST
const res = await pay("https://relay.preflightstack.com/v1/file-slot", {
  method: "POST",
  headers: { "content-type": "application/json" },
  body: JSON.stringify({
    "content_type": "application/pdf",
    "filename": "report.pdf",
    "size_bytes": 18376291
  }),
});
console.log(res.status, await res.text());
Python: pay and call
# pip install "x402[requests,evm]"
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

# Pays at most $0.005 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.005"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.post(
        "https://relay.preflightstack.com/v1/file-slot",
        json={
            "content_type": "application/pdf",
            "filename": "report.pdf",
            "size_bytes": 18376291,
        },
    )
    print(res.status_code, res.text)

Security scan

  • No findings. We scan names, descriptions and tool definitions for hidden instructions and other prompt-injection patterns.

Recent checks

WhenResultHTTPTimePrice
2 h agoPassed402516 ms$0.005
6 h agoPassed402439 ms$0.005
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