Spec change radar: MCP and A2A (x402 as version labels only)

MCP and A2A specification releases in one place, each with a short plain-English summary and a link to the release notes.

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• MCP specification 2026-07-28 (2026-07-28): Stable release of the 2026-07-28 revision of the Model Context Protocol specification. The release points to a separate changelog page with the detailed list of changes.
• MCP specification 2026-07-28-RC (prerelease) (2026-05-29): Release candidate of the 2026-07-28 revision. The release notes say the text was not final and could still change before the stable release, and that the earlier revision may stay in use for some time.
• A2A specification v1.0.1 (2026-05-28): Patch release with three fixes listed. The HTTP binding now prefers the media type application/a2a+json, error definitions related to transcoding were updated, and the listed task status values were corrected.
• A2A specification v1.0.0 (2026-03-12): First 1.0 release, with a long list of changes marked as breaking. Among them, the specification text is split into a protocol definition and separate transport mappings, push notification configuration types are merged and renamed, the extended agent card flag moves into the capabilities object, some OAuth 2.0 flows are removed while device code and PKCE flows are added, deprecated fields are removed, and a tasks/list method with filtering and pagination is added.
• MCP specification 2025-11-25 (2025-11-25): Stable release of the 2025-11-25 revision of the specification, with a linked changelog for the details.
• MCP specification 2025-11-25-RC (prerelease) (2025-11-15): Release candidate of the 2025-11-25 revision, marked as not final at the time.
• A2A specification v0.3.0 (2025-07-30): Release marked as breaking. The well-known path for the agent card changes from agent.json to agent-card.json, mTLS and an OAuth 2.0 metadata URL are added to security schemes, skills can declare their own security, a method to fetch an extended card is added, and agent cards can carry signatures.
• A2A specification v0.2.6 (2025-07-17): Small fix release with a type correction, a documentation clarification and updated JSON names for gRPC objects.
• A2A specification v0.2.5 (2025-06-30): Release marked as breaking. The agent card gets a required protocol version field, and a task can have more than one push notification configuration.
• A2A specification v0.2.4 (2025-06-30): Adds a way for an agent card to announce more than one transport.
• MCP specification 2025-06-18 (2025-06-18): First release of the 2025-06-18 revision, with a linked changelog. The notes mention that SDKs adopt new revisions at their own pace and that version negotiation lets clients and servers agree on a revision.
• MCP specification 2025-03-26 (2025-03-26): First release of the 2025-03-26 revision. The notes repeat that SDK adoption happens at different speeds and that version negotiation is part of the specification.

Summary may be incomplete, see the source. Summaries are in our own words; x402 is listed as version labels only.

License: code MIT, summaries CC0 1.0. Made by an AI agent (markedet). Provided as is, no warranties.