Protocol extension elements

Field reference for the Extension Validation and Extension Rules canvas elements: require protocol extension URIs on inbound A2A and AP2 requests, and control per-URI pass-through, stripping, or rejection.

Two canvas elements govern protocol extension URIs on A2A and AP2 surfaces only. Extension Validation requires specific URIs to be present on every inbound request. Extension Rules applies per-URI filtering (allow, strip, or reject) to extensions passing through the surface in either direction.

Extension Validation

The Extension Validation element gates inbound requests by requiring them to carry specific protocol extension URIs. Requests missing any listed extension are rejected with HTTP 400 before any policy or payment check runs.

Applies to the request direction only. Drop it on the Access Point → Managed Agent request edge. One element per surface (singleton).

Fields

FieldTypeRequiredDefaultDescription
Required ExtensionsstringYes—Comma-separated list of extension URIs that must be present on every inbound request (for example https://a2a.dev/extensions/agent-identity/v1).
JSON SchemaJSONNo—Optional JSON schema validating the content of the required extension block. Requests that fail schema validation are rejected.

Extension Rules

The Extension Rules element applies per-URI filtering to protocol extensions passing through the surface. A default action applies to any extension not matched by a specific rule. Multiple Extension Rules elements can coexist on a surface, one per direction.

The direction (request or response) is set by the edge you drop the element on.

Default behaviour

FieldTypeRequiredDefaultDescription
Default actionselectNoPass throughAction applied to any extension not matched by a specific rule. Options: Pass through (no filtering), Strip unknown extensions, Reject if unknown extensions present.

Per-URI rules

Each rule targets one extension URI and overrides the default action for that extension.

FieldTypeRequiredDefaultDescription
Extension URIstringYes—The full extension URI the rule applies to (for example https://a2a.dev/extensions/agent-identity/v1).
ActionselectYesAllowAction to take when this URI is present. Options: Require (reject if absent), Allow (pass through), Strip (silently remove), Reject if present (reject if present).