Batch attestation

POST /v1/attestations/batch
Authorization: Bearer fmk_...
Content-Type: application/json

{
  "items": [
    { "type": "human", "content": "...", "contentType": "text/article" },
    { "type": "ai", "content": "...", "modelId": "claude-sonnet-4-6", "provider": "anthropic" }
  ]
}

Behavior

• Atomic. EAS doesn’t support partial multicall success: if any item fails resolver validation, the whole batch reverts. Validate inputs carefully before submitting.
• Cap: 100 items per request. Larger batches push gas past Base’s per-tx limit and burn quota on revert.
• Quota: 1 unit per item. A 50-item batch costs 50 attestations from your monthly on-chain bucket. The whole batch is rejected with 429 QUOTA_EXCEEDED if items.length exceeds your remaining quota.
• Order preserved. The uids array in the response is in the same order as your input array.

Response

{
  "uids": ["0xabc...", "0xdef...", "..."],
  "txHash": "0x...",
  "verifyUrls": [
    "https://verify.fidemark.dev/0xabc...",
    "https://verify.fidemark.dev/0xdef...",
    "..."
  ]
}

Gas economics

A batch of N items costs roughly (180k base + N × 200k) × gasPrice. At 100 items and typical Base fees (10 Mwei) that’s ~$0.45 vs ~$0.90 if issued sequentially. The savings grow with batch size.

For very high volume, consider off-chain attestations (SDK → Off-chain): mode: "offchain" per item is unmetered and zero gas, with the option to bring individual envelopes on-chain later.

Errors

Code	Cause
INVALID_INPUT	Body shape wrong, item missing required fields, or count > 100. Error message points at the failing item index.
QUOTA_EXCEEDED	items.length exceeds remaining monthly quota.
VALIDATION_REJECTED	Resolver rejected at least one item: the whole batch reverted on chain.