Use a valid Resource Template expression

Every Resource Template must contain a valid RFC 6570 URI template, even if it has no examples. Correct malformed braces, operators, or variable syntax before checking concrete expansions. The validator does not retrieve the resulting URI.

Requirement

A Resource Template uriTemplate is a valid RFC 6570 URI template.

Details

Rule ID: mcp.resource-template.uri-template
Owner: mcp
Surface: ResourceTemplate · Path: uriTemplate
Kind: embedded-standard
Requirement level: must
Protocol versions: independent of the MCP protocol version
Status: internal · Enforcement: internal

Required by

• MCP Description 0.9.0, Section 10.2.1
  • 10. Resources and Resource Templates: req-resource-template-uri-template

Based on

• Tier 1 — MCP schema.ts and normative specification text: MCP 2024-11-05 to 2026-07-28 schema.ts, interface ResourceTemplate, uriTemplate (“A URI template (according to RFC 6570)”)
  • validation/mcp-schemas/2024-11-05/schema.ts#L456-L461
  • validation/mcp-schemas/2025-03-26/schema.ts#L489-L494
  • validation/mcp-schemas/2025-06-18/schema.ts#L570-L575
  • validation/mcp-schemas/2025-11-25/schema.ts#L846-L851
  • validation/mcp-schemas/2026-07-28/schema.ts#L1482-L1487
• Tier 2 — Normative referenced standards: RFC 6570, URI Template
  • https://www.rfc-editor.org/rfc/rfc6570#section-3

Notes

Reported once per Resource Template, whether or not it has examples; example checks that need the parsed template are skipped.

Examples

Invalid example

Source: expected-invalid/malformed-uri-template-without-examples.json · Selected: /resourceTemplates/0

{
  "uriTemplate": "file:///{path",
  "name": "file_by_path"
}

Invalid example

Source: expected-invalid/malformed-resource-template-example.json · Selected: /resourceTemplates/0

{
  "uriTemplate": "test://items/{id",
  "name": "malformed_template",
  "examples": {
    "concrete": {
      "uri": "test://items/123",
      "result": {
        "resultType": "complete",
        "contents": [
          {
            "uri": "test://items/123",
            "text": "item"
          }
        ]
      }
    }
  }
}

Invalid example

Source: expected-invalid/invalid-completion-example-semantics.json · Selected: /resourceTemplates/0

{
  "protocolVersions": [
    "2026-07-28"
  ],
  "uriTemplate": "repo://{owner/{repository}/issues/{issue}",
  "name": "broken_template",
  "completionExamples": {
    "bad-template": {
      "argument": {
        "name": "issue",
        "value": "12"
      },
      "result": {
        "resultType": "complete",
        "completion": {
          "values": [
            "120"
          ]
        }
      }
    }
  }
}

Rule Source Code

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