> ## Documentation Index
> Fetch the complete documentation index at: https://gofastmcp.com/llms.txt
> Use this file to discover all available pages before exploring further.

# bm25

# `fastmcp.server.transforms.search.bm25`

BM25-based search transform.

## Classes

### `BM25SearchTransform` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/transforms/search/bm25.py#L86" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

Search transform using BM25 Okapi relevance ranking.

Maintains an in-memory index that is lazily rebuilt when the tool
catalog changes (detected via a hash of tool names).