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Group Type

Working Group

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Mission Statement

The Triggers and Events Working Group exists to define how MCP servers proactively notify clients of state changes. Today, clients learn about server-side updates by polling or holding an SSE connection open. This WG will specify a standardized callback mechanism—webhooks or similar—that lets servers push notifications when new data is available, with defined ordering guarantees that hold across all transports.

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Scope

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In Scope

  • Specification Work: SEPs defining the trigger/callback mechanism, subscription lifecycle, delivery semantics, and event ordering guarantees.
  • Reference Implementations: SDK components demonstrating server-initiated notifications and client-side callback handling.
  • Cross-Cutting Concerns: Coordination with the Transports WG on transport-specific delivery behavior, and with the Agents WG where task completion notifications intersect with event triggers.
  • Documentation: Specification sections covering event-driven patterns and migration guidance from polling-based approaches.

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Out of Scope

  • Changes to the transport wire format or session model (owned by the Transports WG).
  • General-purpose pub/sub infrastructure beyond what the MCP protocol requires.
  • Modifications to existing notification primitives (notifications/resources/updated, notifications/tools/list_changed, etc.) that do not relate to proactive server-initiated delivery.
  • Transports WG — delivery and ordering guarantees depend on transport capabilities; callback semantics must be coherent across stdio, Streamable HTTP, and future transports.
  • Agents WG — SEP-1686 (Tasks) identifies webhook-style task completion notifications as a future consideration; this WG owns that mechanism.

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Leadership

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Authority & Decision Rights

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Operations

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Resources

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Deliverables & Success Metrics

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Active Work Items

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Success Criteria

  • An accepted SEP defining the trigger/callback mechanism and its subscription lifecycle.
  • Reference implementations in at least two Tier-1 SDKs.
  • Conformance test coverage for the new primitives.

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Changelog