Persisted queries

Another way to secure the MCP server is to use a safelist of persisted queries as tools for your MCP server.

With persisted queries, clients can send operation identifiers instead of full operations. Additionally, we can configure a safelist of IDs to allow, configured in GraphOS. When you enable safelisting, the router rejects any incoming operations not registered in its persisted query list.

The MCP server can then execute an operation by providing its persisted query ID instead of the entire operation string.

Requesting by ID can significantly reduce latency and bandwidth usage for large operation strings.

Exercise 2: Persisted queries (⏳ 5 min)

Steps

1. Configure the MCP server to use GraphOS-managed persisted queries as the source for tools.

   mcp.yaml

   operations:
     source: uplink

   Copy

2. Configure the router to enable persisted queries.

   graph/router.yaml

   persisted_queries:
     enabled: true

   Copy

3. Restart the rover dev process to pick up the changes. You'll see more new tools load in. Test this new source using MCP Inspector.

Try to run an operation using the execute tool:

The router still accepts it.

1. Configure the router to only allow queries that are in the persisted query safelist.

   graph/router.yaml

   persisted_queries:
     enabled: true
     safelist:
       enabled: true # Router will reject any operations that are not registered in the persisted queries list
     log_unknown: true # Router will log any operations that are not registered in the persisted queries list
   apq:
     enabled: false # to enable safelist, APQs must be disabled

   Copy

   Show code

2. Test this new configuration using MCP Inspector. Use the execute tool and run the same query as before. The router now rejects it.