How much does a pdf-merge call cost?

$0.005 per call, paid in USDC on Base via x402, with no account and no API key.

What does pdf-merge return?

A JSON object with 4 top-level fields: sources, pages, bytes and pdf_base64. The example on this page is a real call over documents/merge-intro.pdf and documents/merge-appendix.pdf.

What happens when a pdf-merge 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 / Documents / PDF Merge API

PDF Merge API

Concatenates 2–8 source PDFs, in order, into one PDF returned base64-encoded. Maximum output PDF size: 25 MiB before base64 encoding.

Endpoint: POST /v1/pdf-merge
Price: $0.005 per call
Family: Documents
Docs: /docs/pdf-merge

01When to use it

Merging PDFs needs a real PDF library and a hardened fetch over several URLs at once: an agent doing it inline walks every one past the SSRF controls, and the joined output must be byte-reproducible.

When not to use it

The input is over 8 MB (8,388,608 bytes): pdf-merge answers too_large (413).
The destination needs more than 45 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
urls	array	yes	The source PDFs, 2 to 8 URLs fetched one at a time and concatenated in this order; each is read up to 8 MiB and an encrypted source is refused.

03Limits

Limit	Value
Size cap	8 MB (8,388,608 bytes)
Timeout	45 s

04Example

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

Request

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

{
  "urls": [
    "https://grist.tools/samples/documents/merge-intro.pdf",
    "https://grist.tools/samples/documents/merge-appendix.pdf"
  ]
}

Response

200 OK
payment-response: <base64 settlement receipt>

{
  "sources": [
    {
      "url": "https://grist.tools/samples/documents/merge-intro.pdf",
      "pages": 1
    },
    {
      "url": "https://grist.tools/samples/documents/merge-appendix.pdf",
      "pages": 2
    }
  ],
  "pages": 3,
  "bytes": 1474,
  "pdf_base64": "JVBERi0xLjcKJYGBgYEKCjQgMCBvYmoKPDwKL0ZpbHRlciAvRmxhdGVEZWNvZGUK..."
}

Sample file: documents/merge-intro.pdf. One-page PDF with a Helvetica text layer introducing a two-part merge, built with pdf-lib with pinned metadata. Sample file: documents/merge-appendix.pdf. Two-page PDF with a Helvetica text layer that closes a two-part merge, built with pdf-lib with pinned metadata.

In documents/merge-intro.pdf, the PDF 1.7 file has 3 top-level objects, 1 object stream among them, and a cross-reference stream; inflated, its streams declare 1 page with MediaBox 0 0 420 300, base font Helvetica and 3 text runs at 14 pt, the first reading "Part One: Introduction". In documents/merge-appendix.pdf, the PDF 1.7 file has 4 top-level objects, 1 object stream among them, and a cross-reference stream; inflated, its streams declare 2 pages with MediaBox 0 0 420 300, base font Helvetica and 4 text runs at 14 pt, the first reading "Part Two: Appendix". In the returned file: the file opens with the header line %PDF-1.7, then a comment of four bytes above 0x7F that marks the file as binary. The first object in the file is number 4, generation 0, a stream compressed with FlateDecode.

Response field	Type	In the example
sources	array	2 items, each with url and pages
pages	number	3
bytes	number	1474
pdf_base64	string	a string of 67 characters

05Call it from code

JavaScript

// pdf-merge: $0.005 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 = {
  "urls": [
    "https://grist.tools/samples/documents/merge-intro.pdf",
    "https://grist.tools/samples/documents/merge-appendix.pdf"
  ]
}

const res = await fetchWithPayment('https://grist.tools/v1/pdf-merge', {
  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

# pdf-merge: $0.005 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 = {
    "urls": [
        "https://grist.tools/samples/documents/merge-intro.pdf",
        "https://grist.tools/samples/documents/merge-appendix.pdf"
    ]
}

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

curl

# pdf-merge: $0.005 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/pdf-merge' -H 'content-type: application/json' -d '{"urls":["https://grist.tools/samples/documents/merge-intro.pdf","https://grist.tools/samples/documents/merge-appendix.pdf"]}'

# 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/pdf-merge' -H 'content-type: application/json' -H 'payment-signature: <base64 x402 payload>' -d '{"urls":["https://grist.tools/samples/documents/merge-intro.pdf","https://grist.tools/samples/documents/merge-appendix.pdf"]}'

06Errors

Code	HTTP	For this service
invalid_input	400	The body does not match the schema; its fields are urls.
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/pdf-merge.

07Questions

How much does a pdf-merge call cost?: $0.005 per call, paid in USDC on Base via x402, with no account and no API key.
What does pdf-merge return?: A JSON object with 4 top-level fields: sources, pages, bytes and pdf_base64. The example on this page is a real call over documents/merge-intro.pdf and documents/merge-appendix.pdf.
What happens when a pdf-merge 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.

08Related

Documents guide