The Bolna knowledge base: how it works, and how to load your knowledge base into it

Bolna gives an AI calling agent its knowledge through RAG on every turn. You upload a PDF or a URL, Bolna cuts it into chunks, and each time the caller speaks, it searches those chunks with the caller's latest message and adds the closest ones to the agent's prompt. There is no mode that gives the agent the whole document.

This page is written from Bolna's own documentation, checked on 25 September 2026. KB Builder is not affiliated with Bolna. Our own live calls so far ran on a different platform, so the advice below applies what we learned there; it has not been tested on Bolna calls yet.

How the Bolna knowledge base works

	What the docs say
Where it lives	Build → Knowledge Base in the dashboard, connected to an agent in its Intelligence tab (previously called LLM)
What you can add	PDF only (up to 20 MB), or a URL to scrape. No Markdown, text or Word files
Retrieval	RAG on every turn, searched with the caller's latest message
Chunk size	512 by default, set when the knowledge base is created (the unit isn't stated)
Overlap between chunks	128 characters by default
Chunks retrieved per turn	15 by default on the create page; another page says 10
Languages	Default or multilingual (100+ languages), chosen at creation and fixed after
Updating	No update option: create a new one and delete the old
Extra charge	None stated; calls are priced per minute

If retrieval fails on a turn, the docs say the agent still answers, without the knowledge base, and the caller never hears an error. That makes silent gaps possible: the agent sounds confident with nothing behind it.

Where it goes wrong on calls

The search uses only the caller's latest words. Callers rarely repeat the product name. After "Tell me about Grade 6", the next question is "And what's the fee?" Searching for "what's the fee" finds fee chunks, and nothing ties them to Grade 6. If a chunk says "₹1,40,000 a year" without naming its grade, the agent can quote it for the wrong one.

Chunks are cut by size, not by meaning. A 512-unit chunk can end between a product's name and its price. With 15 chunks retrieved, the agent often gets several products' details at once and has to guess which belongs to which.

Silent failures. Because a failed retrieval isn't raised, test calls that sound fine can hide a knowledge base that isn't connected or hasn't finished processing.

How to load a KB Builder file into Bolna

A KB Builder knowledge base is a Markdown file written in short sections that each name the product or service they are about, so a chunk still makes sense when it arrives alone. Bolna needs it as a PDF.

1. Convert the file to PDF. Open the Markdown file in any editor that exports PDF, or paste it into a document and save as PDF. Keep the headings and the text as they are.
2. In Bolna, go to Build → Knowledge Base → Add Knowledge Base and upload the PDF on the Upload PDF tab.
3. Choose Language Support: default, or multilingual if callers speak a language other than the website's.
4. Click Upload PDF and wait until the status shows "processed".
5. Open the agent's Intelligence tab, tick the knowledge base under Add knowledge base, and click Save agent.
6. Make test calls that ask a follow-up price question without repeating the product name.

When the business's website changes, rebuild the file, upload the new PDF as a new knowledge base, connect it, and delete the old one so the two versions never compete.

Lines to add to the agent's prompt

These come from our own live calls. The fourth one matters most on Bolna, because search only sees the caller's latest words:

Answer questions about the business only from the knowledge base. If it doesn't have the answer, say you will check, and give the business's phone number.
Give a price, time or rule only from a sentence that names the product or service the caller asked about.
Whenever you give a price, say the name of the product or service with it.
If the caller hasn't said which product or service they mean, ask before answering.
When the knowledge base says something has not been confirmed, say exactly that. Never guess.
Don't promise messages, callbacks or bookings unless the knowledge base says the business offers them.

Settings worth knowing

The chunk size, overlap and number of chunks are fixed when the knowledge base is created through the API (chunk_size, overlapping, similarity_top_k). If you build through the API, a KB Builder file's sections are short, so the default chunk size keeps most sections whole. The dashboard steps above use the defaults.