Chainlink Feed Reader

A broken feed never says so — it returns its last answer formatted exactly like a good one, and contracts that skip the freshness check use it happily. This reads the answer with its proper decimals and then checks the two signals that matter: how long since updatedAt, and whether answeredInRound has fallen behind roundId, which Chainlink documents as a stale-data condition. Flags zero and negative answers as unusable rather than as prices. You supply the aggregator address; none are built in. A feed never reports that it is broken — it returns its last answer formatted exactly like a good one, which is why updatedAt and answeredInRound are the only signals available and why both are checked here rather than just the price.