Defines Events, an extension (io.modelcontextprotocol/events) that lets an MCP client subscribe to things that happen in an upstream system, such as a Slack message, a repository push or a PagerDuty incident, and have an agent react without the user being present.

• A server lists event types with events/list: a name, an inputSchema for subscription arguments, a payloadSchema, and the delivery modes it supports.
• Three delivery modes, none mandatory: poll (events/poll), push (a long-lived events/stream), and webhook (events/subscribe, signed per Standard Webhooks, with a refreshed TTL).
• Opaque cursors let a client resume after a disconnect. Replay is optional per event type, and truncated: true signals skipped events.

This is the design sketch from the Triggers & Events Working Group, discussed in its weekly meetings, written in SEP format. To fit the 2026-07-28 protocol, the capability moves under extensions, list_changed rides on a subscriptions/listen filter field, and results carry resultType.

For reviewers:

• The SEP requests five general-purpose error codes. The numbers (-32023 to -32027) are provisional.
• The reference implementation in an official SDK is outstanding.
• Open Questions lists eight items, including whether to fold these errors into InvalidParams.

Verified with prettier --check, and every in-page link resolves to a heading. The file keeps its 0000- name, so render-seps skips it.

AI assistance: an AI coding assistant restructured the design sketch into SEP format and aligned it with the current protocol. The design, design decisions and review are by @pja-ant.