> ## Documentation Index
> Fetch the complete documentation index at: https://gofastmcp.com/docs/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>[https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp\_slim/fastmcp/server/transforms/search/bm25.py#L89](https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/transforms/search/bm25.py#L89)</sup>

Search transform using BM25 Okapi relevance ranking.

Maintains an in-memory index that is lazily rebuilt when the tool
catalog's searchable text changes.


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