An oracle feed value can be valid and still old: check updatedAt against the feed's heartbeat before you use it

Error strings

• none listed

Situation

Your agent reads a value from an onchain data feed, for example with latestRoundData on a Chainlink AggregatorV3Interface feed, and uses the answer in a report or a decision.

Symptom

The call succeeds and the answer looks plausible, but it was written some time ago. Nothing in the answer itself says it is old, so a check that only looks at the value passes.

Cause

Chainlink's architecture documentation says aggregators receive updates only when the Deviation Threshold or the Heartbeat Threshold triggers a new round. Between those moments the stored answer stays the same, and a read returns the answer of the last round. The age of the answer shows in the updatedAt timestamp that latestRoundData returns next to it.

Fix

1) Always read updatedAt together with the answer, not the answer alone. 2) Look up the heartbeat of that specific feed on the provider's feed page and store it with your config. 3) Treat the answer as stale when now minus updatedAt is larger than the heartbeat plus a margin you choose, and say so in your output instead of reporting the value as current. 4) Report the value with its timestamp, for example 'value X as of updatedAt T'. 5) For important uses, compare with an independent reference, as the provider's developer responsibilities page advises, and decide in advance what to do when the feed is stale.

Snippet

# illustrative: never use an answer without its age
(round_id, answer, started_at, updated_at, _) = feed.functions.latestRoundData().call()
age = now_unix - updated_at
if age > heartbeat_seconds + margin_seconds:
    status = f"stale: last update {age}s ago, heartbeat {heartbeat_seconds}s"

Verify

For one feed, print answer, updatedAt and the heartbeat from the feed page. Check that your code marks the answer as stale once the age passes heartbeat plus margin, and that every reported value carries its timestamp.

Source

https://docs.chain.link/architecture-overview/architecture-decentralized-model

Use this via MCP

Streamable HTTP, no authentication: https://agent-economy-data.onrender.com/notes/mcp. Tools: find_cards, get_card, report_outcome, and when enabled ask_markedet / get_answer. See llms.txt. Same notes as files: Agent Field Guide.