# Help: Vertex AI Search Boost Controls Won’t Accept Custom Field Filters
Hi everyone! 
I’m having trouble with Vertex AI Search boost controls and hoping someone can point me in the right direction.
## What I Want to Do
I have a bunch of PDF documents in my knowledge base, and I want to boost specific ones for certain searches. For example, when someone searches “pricing,” I want my 2025 rate card to always show up first instead of old rate cards from 2023.
## What’s Working
I can create basic boost controls that work fine:
- Boost ALL documents when someone searches “rate card” 
- Boost ALL documents when someone searches “case study”
## What’s Not Working
I can’t target specific documents using their metadata. Every time I try to add a filter like `docType=“rate_card”` to only boost certain documents, I get this error:
```
Invalid filter syntax ‘docType=“rate_card”’.
Parsing filter failed with error: Unsupported field “docType” on comparison operators.
```
## My Setup
- Unstructured data store (PDFs, Excel files)
- Documents have custom metadata fields that show up fine in the schema
- Using the REST API to create controls
## The Question
**Is it actually possible to filter boost controls by document metadata fields?** The documentation suggests it should work, but I can’t get any custom field to be recognized.
Has anyone successfully created boost controls that target specific documents rather than boosting everything for a query term?
## Why This Matters
Right now my search shows old 2023 pricing docs before new 2025 ones, even though the content is identical. Being able to boost by document metadata would solve this instantly.
Any tips, examples, or even just “this doesn’t work yet” would be super helpful!
Thanks! 
**Tags:** vertex-ai-search, discovery-engine, boost-controls, document-filtering