Merge API Documentation

Gateway supports sending PDF documents to models with document input capability. Pass documents as base64-encoded data or a URL, and Gateway handles the provider-specific format translation.

Send a document (base64)

import base64
with open("report.pdf", "rb") as f:
    pdf_data = base64.standard_b64encode(f.read()).decode("utf-8")
response = client.responses.create(
    model="anthropic/claude-sonnet-5",
    input=[
        {
            "type": "message",
            "role": "user",
            "content": [
                {"type": "text", "text": "Summarize this document."},
                {
                    "type": "document",
                    "source_type": "base64",
                    "media_type": "application/pdf",
                    "data": pdf_data,
                },
            ],
        }
    ],
)
print(response.output[0].content[0].text)

AI SDK file parts require merge-gateway-ai-sdk-provider 0.3.0 or later. Earlier versions dropped every file part — documents and images alike — without an error. data may be bytes, a base64 string, a data: URI, or a URL.

Send a document (URL)

URL

response = client.responses.create(
    model="google/gemini-3.6-flash",
    input=[
        {
            "type": "message",
            "role": "user",
            "content": [
                {"type": "text", "text": "What are the key findings?"},
                {
                    "type": "document",
                    "source_type": "url",
                    "media_type": "application/pdf",
                    "data": "https://example.com/report.pdf",
                },
            ],
        }
    ],
)

Supported models

Document input is supported by models with "document" in their capabilities.input array. Check model capabilities via GET /v1/models, or filter by input type in the model catalog.

Documents are estimated at ~1,500 tokens per page for compression calculations. A 10-page PDF counts as roughly 15,000 tokens toward the context window.