An HTTP Status Code to Report Requester Impairment

Introduction This document specifies a Hypertext Transfer Protocol (HTTP) status code for use when a request is denied because the requester is impaired.

Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals, as shown here.

420 Requester Impaired The status code 420 indicates that the server is denying the request as a consequence of evidence of requester impairment. The server in question might not be an origin server. An intermediate proxy closer to the requester may be in a better position to assess potential requester impairment. Such a proxy may refuse to forward the request and respond with this error code. There is no requirement that the requester be human. Certain AI systems can exhibit behaviors such as giving hallucinated, incorrect, and differing answers for a given input. 420 responses MUST include a Link header with a relation type of "status". This link is used by the remediated requester to obtain information about the server state and to signal to the server that the requester is remediated. Requesters SHOULD use this link when remediated before making subsequent requests unless a bearer token is used as described under and the server does not require usage of the link. A 420 response is non-cacheable by default, i.e., unless otherwise indicated by the method definition or explicit cache controls; see .

AI: An artificial intelligence system that is capable of making independent decisions without direct human control.
proxy: A server with a primary purpose of forwarding requests to other servers to process.

Example Response in Problem Details Format ; rel="status" Content-Type: application/problem+json Content-Language: en { "type": "https://example.com/erratic-requests", "title": "Requester Impaired: Erratic Behavior Detected.", "detail": "Erratic requests detected." } ]]>

IANA Considerations IANA is asked to update the HTTP Status Codes Registry with the following entry:

Code: 420
Description: Requester Impaired
Specification: This RFC

Security Considerations The usage of the link resource provided by the Link header to assert requester remediation assumes a requester or proxy that is trustworthy enough to halt requests and only access the link resource after requester remediation. If greater security is required, perhaps to enable an external system to remediate and validate the requester, a server MAY require an OAuth authorization bearer token to signal remediation of the requester. If a valid bearer token is required and missing, further requests SHOULD be rejected with a 403 Forbidden response code with the insufficient_scope error code and scope attribute naming the authorization token required as described in section 3.1. Once this authorization bearer token is validated the server MAY allow requests without using the Link provided in the 420 response, but MUST NOT respond to usage of the link as an error.