Protocol extension elements

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

Two canvas elements govern protocol extension URIs on A2A 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 lets you configure a list of protocol extension URIs that inbound requests are expected to carry, with an optional JSON schema for their content.

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

Fields

Field	Type	Required	Default	Description
Required Extensions	string	Yes	—	Comma-separated list of extension URIs the element is configured to require on every inbound request (for example `https://a2a.dev/extensions/agent-identity/v1`).
JSON Schema	JSON	No	—	Optional JSON schema for validating the content of the required extension block.

Extension Rules

The Extension Rules element lets you configure per-URI filtering (allow, strip, or reject) for protocol extensions passing through the surface, with a default action for 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

Field	Type	Required	Default	Description
Default action	select	No	Pass through	Action for 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.

Field	Type	Required	Default	Description
Extension URI	string	Yes	—	The full extension URI the rule applies to (for example `https://a2a.dev/extensions/agent-identity/v1`).
Action	select	Yes	Allow	Action for this URI. Options: Require (reject if absent), Allow (pass through), Strip (silently remove), Reject if present.

Managed Agent reference: canvas element overview.
Access Point reference: inbound surface configuration.

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