RPC

The nine read-only JSON-RPC tools: block, balance, gas, receipt, and contract-source lookups.

Every one takes a chain slug — ethereum, base, robinhood, or base-sepolia — not a numeric chain id. The slugs come from packages/chains, the single registry in the stack that defines a chain id, so an id you have not heard of fails validation instead of being sent to a chain that does not exist.

Which tools a chain supports is a per-chain capability flag in that same registry, not a branch inside a tool.