A large dataset can still be unusable if it omits delisted securities, rewrites historical fundamentals with the latest restatement, or cannot explain a missing session. Define the decision the data must support and the historical information boundary before comparing vendor totals.
For price research, specify the universe, exchange calendar, interval, adjustment view, and corporate-action treatment. For event research, specify which filings, earnings records, news references, or macro series must be observable by a given known-at cutoff. These requirements turn a vague data purchase into a testable acceptance plan.
- List required and optional fields separately.
- Define the earliest and latest eligible timestamps.
- State whether corrections may rewrite prior exports.
- Set a maximum unexplained-gap rate before evaluation.