Add an MCP endpoint to search the Solr ref guide by version

[jzonthemtn]

Add an MCP endpoint to search the Solr ref guide by version. For example, the user should be able to request "circuit breakers" and Solr 9.10 and return the URLs of relevant ref guide pages.

Note that the MCP endpoint doesn't return blocks of text, but instead it returns URLs of relevant Solr ref guide pages.

Please make sure that approach sounds ok and feel free to assign to me and I'll make a PR.

[jzonthemtn]

Talked with @epugh and would like to be able to handle older versions of the Ref Guide prior to 9.0 which are PDFs (https://archive.apache.org/dist/lucene/solr/ref-guide/).

[adityamparikh]

Hi Jeff @jzonthemtn,

Thanks for the PR #86. It became easier to understand what you're trying to accomplish. Listing a few considerations -

Server scope: The primary concern of this MCP server is interacting with a running Solr instance. A ref guide lookup doesn't interact with the user's Solr deployment; it's documentation retrieval, which would be a different concern.

Context7: Solr documentation lookup is already available via https://context7.com/apache/solr, whose primary purpose is providing up-to-date library documentation to LLMs. Users can configure Context7 alongside this MCP server today.

Approach: Parsing XML from the Solr website sitemap via a remote call that is not an API endpoint would be brittle. More importantly, returning URLs would not helpful to an LLM since it has no browser to follow them.

MCP clients with web search/fetch capabilities: These LLMs can already navigate to solr.apache.org/guide directly and find relevant documentation on their own — the tool becomes a redundant middleman.
MCP clients without web search/fetch: For these, returning URLs is even less useful since there's no way to follow them. To be genuinely helpful in this scenario, the tool would need to fetch the matched pages and return actual content excerpts — but at that point we're reimplementing what Context7 already does.

If we are seeing cases where LLM in an MCP client is not able to invoke the right tool correctly, perhaps we can try improving the tool description?

MCP Resource: If the goal is to give the LLM more context about specific Solr instance to help it use tools correctly, @McpResource with URI templates (e.g. solr://collections/{name}/schema) would be the right MCP primitive for exposing contextual data about the specific Solr instance — schema, config, cluster state. That's distinct from general-purpose documentation, which would belong in a documentation server like Context7.