The problem: supported somewhere is not the same as supported by the right source What ProvenanceGuard does Results Checking claims when sources look similar Repairing blocked answers Why this fits Multiverse Computing Tool-using LLM agents no longer read from a single retrieved passage. Through the Model Context Protocol (MCP), an agent can call a search tool, inspect a structured patient or account record, query a database, and pull metadata, then weave all of it into one answer. That m aakes the usual question of factuality more subtle than it looks. Most of the systems built to check LLM answers, from RAGAS faithfulness to fine-grained checkers like MiniCheck, AlignScore, and SummaC, ask whether a claim is supported by the available evidence once that evidence has been pooled together. In their usual form, they do not tell us which MCP tool output supports each claim, or whether that is the source the answer names.