Use Resource Contents metadata where supported

Resource Contents entries acquire _meta from MCP 2025-06-18. This is separate from result-level _meta, which is available in every supported version. Move or remove a misplaced value only after deciding which object it describes.

Requirement

Resource contents carry _meta only from MCP 2025-06-18, in Resource examples and in embedded resources.

Details

Rule ID: mcp.resource-contents.meta.protocol-version
Owner: mcp
Surface: ResourceContents · Path: _meta
Kind: structural
Requirement level: must
Status: internal · Enforcement: internal

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

• MCP Description 0.9.0, Section 10.4.4
  • 10. Resources and Resource Templates: req-resource-contents-meta

Based on

• Tier 1 — MCP schema.ts and normative specification text: MCP 2024-11-05 and 2025-03-26 schema.ts, interface ResourceContents (uri, mimeType); MCP 2025-06-18 to 2026-07-28 schema.ts, interface ResourceContents (adds _meta)
  • validation/mcp-schemas/2024-11-05/schema.ts#L483-L497
  • validation/mcp-schemas/2025-03-26/schema.ts#L521-L535
  • validation/mcp-schemas/2025-06-18/schema.ts#L600-L621
  • validation/mcp-schemas/2025-11-25/schema.ts#L876-L897
  • validation/mcp-schemas/2026-07-28/schema.ts#L1509-L1527

Examples

Invalid example

Source: expected-invalid/resource-example-result-semantics.json · Selected: /resources/1/examples/unsupported-metadata/result/contents/0

{
  "uri": "test://legacy",
  "text": "legacy",
  "_meta": {
    "unsupported": true
  }
}

Rule Source Code

content.yaml at immutable tag v0.9.0-rc.3.