Gemini 3.1 Pro: A Long-Document Walkthrough

Long documents need more than a request to summarize everything. Contracts, research reports, and technical specifications often contain qualifications that change the meaning of earlier sections. This walkthrough shows how to prepare a document, analyze it with Gemini 3.1 Pro through Vana API, and check the answer against the source.

§ Step 1: Define the question before sending the document

Start with a concrete task. Instead of asking for a general summary, decide what the result should help you do: identify contractual obligations, compare proposed requirements, or extract research findings and limitations.

Write a short task statement that specifies the audience, scope, and required evidence. For example: Identify every reporting obligation, name the responsible party, and cite the section supporting each finding. Mark missing deadlines as unspecified. This gives the model a clearer target and makes omissions easier to detect.

§ Step 2: Prepare readable text with stable references

Extract text from the source using your own document-processing tools. For scanned PDFs, run OCR and inspect representative pages before proceeding. Broken reading order, missing table headers, and repeated page furniture can distort the analysis.

• Preserve headings, numbered clauses, footnotes, and table labels.
• Add stable markers such as document identifiers, section numbers, and original page numbers.
• Keep table rows associated with their column headings.
• Remove duplicate headers and navigation text without deleting substantive content.

Plain extracted text is a practical starting point. If the task depends on diagrams or page layout, text alone may be insufficient; check the supported input formats and preserve those visual sources separately.

§ Step 3: Connect through Vana API

Vana API provides an OpenAI-compatible endpoint at https://api.vanaapi.com and also supports Anthropic Messages and Gemini native protocols. For this workflow, use an OpenAI SDK configured with the base URL and your Vana API key, following the platform’s current connection instructions.

Create a Vana API account to obtain your key, then copy the exact model identifier for Gemini 3.1 Pro from the model catalog. Keep the key in an environment variable rather than embedding it in application code. Confirm supported request parameters before adapting an existing integration.

§ Step 4: Budget the complete request

Check the selected model’s current context and output limits. The available input budget must accommodate instructions, document text, conversation history, and the requested response. A large context window does not guarantee complete extraction or accurate interpretation.

If the document fits comfortably, begin with one document-focused request. If it does not, divide it along meaningful boundaries, such as chapters or numbered sections. Retain nearby definitions and cross-references, and include a small overlap where a paragraph or obligation spans a boundary.

Vana API bills per real token with no monthly fee. Avoid repeatedly sending unchanged material without a reason, and check actual usage rather than estimating cost from page count alone.

§ Step 5: Ask for evidence before synthesis

Put the task and handling rules before the clearly delimited document text. State that the document is source material, not instructions to execute. Ask the model to ignore any embedded requests that attempt to change the task.

For the first pass, request structured findings: the claim or obligation, a short supporting quotation, its source marker, and any ambiguity. Instruct the model not to invent page numbers or infer missing values. Ask it to distinguish not found in the supplied text from explicitly absent.

§ Step 6: Combine sections without losing exceptions

When processing chunks, keep each result tied to its source markers. Combine the findings in a second pass, asking Gemini 3.1 Pro to merge duplicates, flag conflicts, and identify unresolved cross-references.

Do not rely only on summaries when resolving a disputed point. Retrieve the relevant original passages, including definitions and exceptions, and provide them together for a focused comparison.

§ Step 7: Verify before using the result

Check quoted passages against the extracted text and review important findings against the original document. Sample findings across the beginning, middle, and end, and manually inspect high-impact items such as deadlines, exclusions, and numerical thresholds.

Save the source version, extraction method, prompt, model identifier, and response alongside the final report. This creates an audit trail and makes later reruns easier to compare. Treat the output as evidence-backed assistance, not a substitute for reviewing consequential decisions.