- Replace Open Question 6 with normative endpoint-verification rules:
a mandatory intent challenge (or allowlist) before activating webhook
delivery, cached per (principal, url); add -32014 EndpointVerificationFailed
and fill the verification control-envelope row.
- Add optional asymmetric server signing (Standard Webhooks v1a,) for
known-server allowlists. The webhook-signing key is discovered from an
origin the client already authenticates: inline webhooks.signingKeys on
the SEP-2127 server card if it lands first, otherwise a standalone
/.well-known/mcp-webhook-jwks.json document (one chosen at SEP-review time).
- Correct the webhook-secret rationale (HMAC stops deception, not flooding)
and add Key Design Decisions rows for endpoint verification and server identity.
- Add a Threat Model summary table to Security Considerations.
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