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SKILL.md
npx skills add hedera-dev/hedera-skills --skill chainlink-data-feeds
Chainlink Data Feeds on Hedera. Use when reading AggregatorV3 price feeds on Hedera (testnet 296 / mainnet 295), calling latestRoundData, checking round completeness and staleness, or normalizing feed decimals. Not for Chainlink CCIP (cross-chain tokens).
npx skills add hedera-dev/hedera-skills --skill chainlink-data-feeds
Push feed pattern: a Chainlink aggregator is updated off-chain; on-chain readers call latestRoundData() and must reject incomplete, non-positive, or stale rounds.
Consumers may wrap the feed behind a local interface; that is optional. Do not assume a project-specific adapter name.
| Piece | Role |
|---|---|
AggregatorV3Interface | latestRoundData() + decimals() |
| Round completeness | answeredInRound >= roundId and updatedAt != 0 |
| Price | answer > 0 (feeds are typically signed int256) |
| Freshness | Compare block.timestamp - updatedAt to a max staleness |
| Scale | Normalize feed decimals to the consumer’s scale (often 18) |
| Pair identity | Prefer canonical uppercase symbols (HBAR, USD) if you hash pair keys |
Hedera chain IDs: testnet 296, mainnet 295.
See references/hedera-feeds.md for where to source Hedera feed addresses. See references/examples.md for read and normalize sketches.
Never return a price from a missing or unfinished round. Revert when:
| Condition | Why |
|---|---|
answeredInRound < roundId | Aggregator has not finished this round |
updatedAt == 0 | No successful update |
answer <= 0 | Invalid / non-positive price |
block.timestamp - updatedAt > maxStaleness | Stale for this consumer |
Do not copy Ethereum mainnet aggregator addresses onto Hedera. Look up Hedera-specific Data Feed addresses for chain 295 / 296 and re-check docs before mainnet.
Pair maps (if you use them) should be constructor-only unless the project explicitly supports post-deploy updates.
feed.decimals() is often 8. Convert to the scale your app uses before arithmetic:
Keep conversion rounding explicit (usually round down). Do not mix raw aggregator units with 18-decimal amounts.
When implementing or reviewing Chainlink reads on Hedera:
latestRoundData completeness checks before using answer295 or 296 (or the project’s documented Hedera network)latestRoundData and normalize sketchesuint256 price = normalizeToScale(uint256(answer), feed.decimals(), /* target */ 18);