Add docs for new thv run --tools flag.

This change adds a small section under the "Run MCP servers" page
documenting how to filter tools exposed by a server.

Fixes stacklok/toolhive#1007

Author: blkt

docs/toolhive/guides-cli/run-mcp-servers.mdx

@@ -142,6 +142,36 @@ specific proxy port instead, use the `--proxy-port` flag:
 thv run --proxy-port <PORT_NUMBER> <SERVER>
 ```
 
+### Run a server exposing only selected tools
+
+ToolHive can filter the tools returned to the client as result of a `tools/list`
+command as well as block calls to tools that the user did not want to expose.
+
+This can help reduce the amount of tools sent to the LLM while still using the
+same MCP server, but it is not meant as a security feature.
+
+To filter the list of tools, use the `--tools` flag either once
+
+```bash
+thv run --tools <TOOL_1>,<TOOL_2> <SERVER>
+```
+
+Or multiple times
+
+```bash
+thv run --tools <TOOL_1> --tools <TOOL_2> <SERVER>
+```
+
+For example:
+
+```bash
+thv run --tools list_issues,get_issue github
+```
+
+If the server comes from the registry, ToolHive can validate the tool names
+against the list advertised in the image reference. An error is returned in case
+ToolHive cannot find one of the tools specified by the user.
+
 ## Run a custom MCP server
 
 To run an MCP server that isn't in the registry, you can use a