1. Define the number before searching
“The price” may mean a last trade, an index, a reference rate, a midpoint or a volume-weighted calculation. “Volume” may count spot trades, derivatives, one venue or an aggregated set. Begin by defining the field, asset, quote currency, market type and time window.
An article that compares sources without these definitions can create false disagreement. Save the API or page endpoint, query parameters and retrieval time. A chart title is not a methodology.
2. Timestamps have a timezone and a clock
Market data can use exchange time, UTC, block time or the viewer's browser clock. A daily candle on one service may close at a different UTC boundary from another. Convert timestamps explicitly and retain the original value. A price retrieved at 12:00 UTC is not the same observation as a price retrieved at 12:05 during a volatile period.
For historical comparisons, record whether the source revises candles, removes erroneous trades or publishes a fixed snapshot. Do not compare an unrevised live endpoint with a later corrected dataset without explaining the difference.
3. Venue coverage changes the result
Aggregators select venues, weight them and filter outliers according to their methodology. An exchange's own price reflects its order book and trading rules. Neither is automatically the universal price. Thin markets can show a large last trade that does not represent the depth available to a typical user.
List the venues and weighting rule when the distinction affects the conclusion. Use a deep, independently documented source for a reference rate. Avoid quoting a single illiquid venue as evidence of a global market move.
4. Volume and market cap are derived fields
Volume can be reported in base units, quote currency or contracts. Derivatives volume may count notional exposure rather than coins changing hands. Market capitalization multiplies a price by a supply definition that may include circulating, total or an issuer-reported figure. Different definitions produce different numbers.
State the source's supply methodology and whether it excludes locked, burned or disputed balances. Do not add volumes from overlapping aggregators. Preserve the unit and decimal precision in your notes.
5. Reproduce the claim instead of trusting a screenshot
A reproducible data note includes source URL, asset identifier, quote, venue list, interval, timezone, retrieval time, filtering and rounding. If an API requires a key, do not publish it. Capture a small response sample without personal account data and keep a hash or archive according to your editorial policy.
When a source changes its endpoint or methodology, update the article and mark the break in the time series. A smooth-looking chart can hide a change in provider coverage.
Worked example: two “daily highs”
Source A defines a daily candle in UTC and aggregates ten spot venues; Source B follows one exchange's local session. During a sharp move near midnight UTC, their daily highs differ. Neither number is automatically an error. An accurate report names both definitions and avoids claiming that one source disproves the other.
The same discipline applies to stablecoin prices, where a small deviation may appear larger on a thin venue.
FAQ
Is an exchange API more accurate than an aggregator?
It is more direct for that exchange's market, but it does not describe every venue or an index methodology. Choose the source that matches the question and state its limits. Do not turn a data vendor's methodology into an investment forecast.
Practical record for this topic
Save the raw response or a permitted excerpt alongside the query parameters, units, decimal precision, timezone and retrieval time. If the provider changes venue coverage, split the series or add a visible break rather than joining unlike data. When rounding for a headline, retain the unrounded value in the notes. Readers can then reproduce the observation and understand why a different provider may publish another value. Also note the endpoint version and any documented rate limits, because a partial response can resemble a quiet market.