Task capabilities from MCP 2025-11-25 and extension advertisements in MCP 2026-07-28 are not interchangeable fields. Limit each capability declaration to the versions that define it. The validator does not automatically translate a tasks object into an extension advertisement.
Requirement
Section titled “Requirement”The core tasks server capability exists only in MCP 2025-11-25; MCP 2026-07-28 uses the tasks extension instead.
Details
Section titled “Details”Rule ID: mcp.capabilities.tasks.protocol-version
Owner: mcp
Surface: ServerCapabilities · Path: tasks
Kind: structural
Requirement level: must
Status: internal · Enforcement: internal
Protocol version applicability
Section titled “Protocol version applicability”2024-11-05 |
2025-03-26 |
2025-06-18 |
2025-11-25 |
2026-07-28 |
|---|---|---|---|---|
| applies | applies | applies | applies | applies |
Required by
Section titled “Required by”- MCP Description 0.9.0, Section 8.3
- 8. Capabilities: req-capabilities-tasks-distinct
-
- Versioning: req-field-protocol-version-availability
Based on
Section titled “Based on”- Tier 1 — MCP schema.ts and normative specification text: MCP 2025-11-25 schema.ts, ServerCapabilities tasks; MCP 2025-06-18 and 2026-07-28 schema.ts, ServerCapabilities (no tasks)
Examples
Section titled “Examples”Invalid example
Section titled “Invalid example”Source: expected-invalid/tasks-capability-2026.json · Selected: /capabilities/0
{ "tasks": { "list": {} }}Rule Source Code
Section titled “Rule Source Code”capabilities.yaml at immutable tag v0.9.0-rc.3.