agent-exec URL Attestation (POST /attest)

x402

agent-exec URL Attestation (POST /attest) is a paid API for AI agents from agent-exec.448c.net, paid per call via x402, $0.008/call, status unknown (last checked 2026-10-11).

Fetches a URL from the service's vantage point and returns a cryptographically signed attestation of the HTTP response metadata, including status code, content hash, and redirect chain.

Price / call$0.008

Seller volume →—

Success—

StatusUnknown

How this service works

Accountless, pay-per-use code execution for software agents: submit source code, get stdout, stderr and exit code back from an isolated, network-less sandbox. No account, no API key -- possession of valid payment is sufficient.

Output

A signed attestation object containing: attestation_id, the original URL, observed_at timestamp, fetch_ok boolean, fetch_code, HTTP status code, SHA-256 hash of the response body, body byte count, truncation flag, content-type, final URL after redirects, redirect count, and an EIP-191 personal-sign signature from the attesting signer_address. On success, also includes payment metadata (asset, payer address, amount, network, transaction hash). The signature can be verified with viem's verifyMessage under the 'agent-exec attestation v2' domain.

Example use cases

Prove API endpoint availability

“I need a cryptographically signed proof that https://api.myservice.com/health returned a 200 OK right now — something I can show to a client as third-party verification.”

Verify content integrity of published file

“Fetch https://releases.myproject.org/v2.1/binary.tar.gz and give me an attestation with the SHA-256 hash of the body, so I can confirm the file hasn't changed since we published it.”

Detect unexpected redirects

“Check whether https://mystore.com/checkout still resolves directly or if it's been redirected somewhere unexpected — I want a signed record of the final URL and the redirect chain.”

Technical details

Endpoint

POSThttps://agent-exec.448c.net/attest?utm_source=zero.xyz

When to prefer

Choose this endpoint when you need a cryptographically verifiable, third-party attestation of a URL's HTTP response metadata (status, content hash, redirects) rather than just fetching the content yourself. It is especially valuable when you must prove to an external party — possibly on-chain — that a URL was reachable and had specific content at a given moment. Note: the response body itself is never returned; only metadata and a signed hash are provided. Prefer this over self-fetch when neutrality, non-repudiation, or external-vantage-point checking matters.

Side effects

fetch_ok=false if the URL has a DNS failure, connection timeout, or SSRF-unsafe redirect — detail field explains the reason
Non-existent or unreachable domain returns fetch_ok=false with a DNS/connect error detail
Redirects to private/internal IP ranges are refused for SSRF safety
Payment failure results in HTTP 402 before the fetch is attempted
URL exceeds 2048 UTF-8 bytes returns a validation error
Body truncated at 1 MB — body_truncated=true if the resource is larger

Input

Schema · Request body

Field	Type	Description
urlrequired	string	An absolute http:// or https:// URL, at most 2048 UTF-8 bytes. Fetched from OUR vantage point; the body is never returned to you.

Output

Schema · Response

Field	Type	Description
urlrequired	string	The URL you asked us to fetch, exactly as sent.
detailrequired	—	Free-text detail on a non-OK fetch_code (e.g. the timeout budget, the unsafe redirect target). Null when fetch_ok is true.
payment	object	Only present on POST /attest's 201, never on a GET /attest/{id} read.
fetch_okrequired	boolean	Whether the fetch reached a real HTTP response, however unsuccessful. false means DNS/connect failure, timeout, or a redirect refused for SSRF safety -- see fetch_code.
redirectsrequired	integer	How many redirects were followed before the final response (or the refusal).
signaturerequired	string	An EIP-191 personal-sign signature over attestation_id, url, final_url_after_redirects, observed_at, http_status, body_sha256, body_bytes, body_truncated, content_type, fetch_ok, fetch_code and redirects (domain "agent-exec attestation v2"), from signer_address. `detail` and `signer_address` are NOT part of the signed message. Verify with viem's verifyMessage({address: signer_address, message, signature}) -- see GET /attest/{id}'s description for the exact message and for handling an attestation signed under the prior v1 domain.
body_bytesrequired	integer	Bytes actually read off the wire, capped at 1048576 per fetch -- see body_truncated.
fetch_coderequired	string
body_sha256required	—	sha256 of the fetched body, hex-encoded, or null if fetch_ok is false. The body itself is never returned or stored beyond this hash.
http_statusrequired	—	The HTTP status the final hop answered with, or null if fetch_ok is false.
observed_atrequired	string	When the fetch completed, ISO 8601.
content_typerequired	—	The Content-Type header on the final response, or null if fetch_ok is false.
attestation_idrequired	string	Pass as GET /attest/{id} to read this back, or hand it to a third party to verify.
body_truncatedrequired	boolean	True if the body was larger than the per-fetch cap and body_sha256/body_bytes cover only the truncated prefix.
signer_addressrequired	string	The address that signed this attestation. Also published at GET /health as attestSignerAddress, if you lost track of which address to verify against.
final_url_after_redirectsrequired	—	The URL actually fetched after following redirects, or null if the fetch never reached one.

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