> ## Documentation Index
> Fetch the complete documentation index at: https://blog.pig4cloud.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Mcp register

[https://blog.modelcontextprotocol.io/posts/2025-09-08-mcp-registry-preview/](https://blog.modelcontextprotocol.io/posts/2025-09-08-mcp-registry-preview/)

## MCP Registry client

LangChain4j also offers a separate client implementation that can talk to
[MCP registries](https://registry.modelcontextprotocol.io/docs#/). Right now, only
read-only operations are implemented (you can search for MCP servers, but managing and adding servers
is not supported - please use the
[official tools](https://github.com/modelcontextprotocol/registry/blob/main/docs/guides/publishing/publish-server.md) for that).

***WARNING:*** Discovering MCP servers and using them (especially running locally) may present serious security risks. Before
running any MCP server that you locate in a public registry, make sure you can trust it.

The registry client
lives in the `dev.langchain4j.mcp.registryclient` package and can be initialized like this:

```java theme={null}
McpRegistryClient client = DefaultMcpRegistryClient.builder()
        .baseUrl("URL-OF-THE-REGISTRY")
        .build();
```

If no base URL is provided, the official registry will be used as the default ([https://registry.modelcontextprotocol.io](https://registry.modelcontextprotocol.io)).
Then, to search for MCP servers, use the `registry.listServers(McpServerListRequest)` method. A `McpServerListRequest`
object can be built using the `McpServerListRequest.Builder` class. The Java API in LangChain4j
closely mirrors the REST API of MCP registries as described in the official
[MCP Registry Reference](https://registry.modelcontextprotocol.io/docs).