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Two terms appear throughout these docs:
  • A source is an API definition: a URL, how to call it, and how to extract one value. It is identified by its sourceId, the hash of its canonical config.
  • A feed is a Solana Feed account holding the latest verified value that one submitter wrote for a source at one quorum.
There is no feed-creation step. A source exists as soon as you define it, and a Feed account is created the first time someone submits an attestation for it.

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API config

aggregation is optional and switches the source to tolerance mode. All fields are listed in the SDK reference.

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Source ID

  • The same config gives the same sourceId for everyone, on every chain. It contains no owner, payer or quorum.
  • The canonical form is not RFC 8785 (JCS). Derive it with the SDK (deriveSourceIdString(apiConfig)) or the MCP derive_source_id tool rather than hashing by hand: one differing byte gives a different source.
  • The gateway and the nodes recompute it from the apiConfig you send, and the SDK rejects a response that names a different sourceId.

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Private configs

Only the sourceId reaches the chain. An API key can stay private: reference it as {{secret.<name>}} in the config and send the value encrypted for the nodes, so the gateway never sees it. Encrypted secrets work on subscription rounds only. See Private APIs.

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Exact and tolerance mode

By default a round is exact: every signing node must fetch a byte-identical value. Design exact sources around settled data:
  • Prefer finalized values over live-drifting ones.
  • Avoid per-request timestamps, request IDs and unstable ordering in the response.
  • Point responseParser at exactly the field you need.
For numeric values that move between fetches, use tolerance mode. The nodes share their observations, drop outliers and sign the median:
  • aggregation is part of the sourceId, so a source’s tolerance settings cannot change without changing its identity.
  • The round needs signaturesRequired of at least 3.
  • The signed value is a two’s-complement int256 scaled by 10^decimals. Leave valueTransform empty.

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Values

The signed value is always 32 bytes. Its meaning is defined by whoever designs the source:
  • Numeric sources should document their scale, for example value / 10 ** 6.
  • A value longer than 32 bytes is signed as its keccak256 hash. The submitter can pass the preimage (up to 256 bytes) to submit_attestation, which checks it and marks the feed Hash. The preimage is not stored.
  • Decode a value only after verifying the attestation or validating the Feed account address.

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Solana feed account

Each submitter maintains its own account for a source and quorum, so a reader decides whose feed it reads. The program re-verifies every write, so a submitter cannot change a value. It only chooses which attestations to submit and when. Reading a feed is free and needs no subscription. Verify on Solana shows how to read one from TypeScript or from your own program.