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

# Similarity Search

> Similarity Search is an automated part of the code review process that finds the patterns, implementations and definations to verify the code implemented is correct

<Note>
  Similarity Search is only available on PRO plan.
</Note>

## Overview

Similarity Search is an automatic review step that compares every new or modified function call **in your pull request** with existing definitions across the repository.\
It then checks whether the way the engineer is *using* that function matches the original implementation’s contract (required parameters, return value, side-effects, etc.).

When a mismatch is detected, the reviewer leaves an inline suggestion that pin-points:

1. The **issue** – what is being mis-used and why.
2. The **fix** – the minimal code change required to align the call-site with the definition.
3. The potential **impact** if the mismatch is shipped.

> **Example**
> The screenshot below shows `isValidUrl` being invoked with two parameters even though its definition only accepts one.
> Similarity Search detected the mismatch and suggested the one-line fix.

<Frame>
  <img src="https://mintcdn.com/gravitycloud-9ebb5c50/3U87DakErDeBshmz/images/features/similarity-search.png?fit=max&auto=format&n=3U87DakErDeBshmz&q=85&s=fc692cfd43871c5b2bce6b804c1d5cfa" alt="Similarity Search" width="1640" height="1096" data-path="images/features/similarity-search.png" />
</Frame>

## How it works

We use [ast-grep](https://github.com/ast-grep/ast-grep) for syntax-aware matching between new or modified call-sites and existing symbol definitions across the repository.

## Why you’ll love it

* **Catch bugs early** – Prevent invalid API usage before it reaches CI.
* **Shorter reviews** – Focus human reviewers on architectural decisions, not boilerplate mistakes.
* **Faster onboarding** – New engineers quickly learn correct library usage by example.

## Enable / disable

Similarity Search is **on by default** for all repositories. You can use the setting `Enable Similarity Search` option in the MatterAI configurations to enable or disable it.

## Supported languages

* JavaScript / TypeScript
* Python
* Go
* Java
* Kotlin
* Python
* C# / C++
* Rust

## Limitations & future work

* Only analyses intra-repository symbols today, cross-repo support is on the roadmap using Semantic Search.