## State witness for a block `GET /v1/proofs/witness/{index_block_hash}` The block's MARF state witness (wire v3) from the proof sidecar: the trie nodes the block wrote, ancestor roots, and the names of every write. Recompute the root and compare it with the header's `state_index_root`; every changed leaf is a named write, a carried value, or an internal key, so a hidden write fails. Extracted on demand, so it has its own lower rate limit. Free and keyless: never metered, no account needed. Hosted limits: 10 requests per second per IP (1 for witnesses), or 20 (2) per account with a key. Bytes are passed through unchanged; verify them, do not trust them. ### Path parameters | Name | Type | Description | | --- | --- | --- | | `index_block_hash` | string, required | The block's `index_block_hash`: 64 hex characters, `0x` optional. | ### Responses - `200` The witness bytes. Immutable. - `400` A path or query parameter is malformed (`VALIDATION_ERROR`): hashes must be exact-length hex, heights non-negative integers - `401` This bind requires the instance token, and it was missing or wrong - `404` The sidecar has no block with that `index_block_hash` - `429` Rate limited; retry after `Retry-After` seconds - `502` The node or proof sidecar could not be reached, or answered with an unexpected status (`PROOF_SOURCE_ERROR`) - `503` `PROOFS_UNAVAILABLE`: this instance has no proof sidecar (`PROOF_SIDECAR_URL` unset). `PROOF_SOURCE_BUSY`: the sidecar is busy; retry after `Retry-After` seconds ### Example ```bash curl https://api.secondlayer.tools/v1/proofs/witness/990152a894e12288960c8b68e5790ad7994f9d261e9ad8adc13c72e76f914339 \ -H "Authorization: Bearer $SECONDLAYER_API_KEY" ```