Resource annotations exist in early MCP protocol versions, but lastModified was added in 2025-06-18. If a declaration covers an earlier version, omit lastModified or describe separate variants with disjoint scopes.
Requirement
Section titled “Requirement”Resource Annotations carry lastModified only from MCP 2025-06-18, on declarations and on content blocks.
Details
Section titled “Details”Rule ID: mcp.annotations.last-modified.protocol-version
Owner: mcp
Surface: Annotations · Path: lastModified
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 10.3
- 10. Resources and Resource Templates: req-resource-annotations-last-modified
Based on
Section titled “Based on”- Tier 1 — MCP schema.ts and normative specification text: MCP 2024-11-05 and 2025-03-26 schema.ts, annotations (audience, priority); MCP 2025-06-18 to 2026-07-28 schema.ts, interface Annotations (adds lastModified)
Examples
Section titled “Examples”Invalid example
Section titled “Invalid example”Source: expected-invalid/annotations-last-modified-before-2025-06-18.json · Selected: /resources/0/annotations
{ "priority": 0.5, "lastModified": "2025-05-03T14:30:00Z"}Rule Source Code
Section titled “Rule Source Code”annotations.yaml at immutable tag v0.9.0-rc.3.