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Version: 0.49.0

MCP-014: Invalid outputSchema Definition - MCP

Summary​

  • Rule ID: MCP-014
  • Severity: HIGH
  • Category: MCP
  • Normative Level: MUST
  • Auto-Fix: No
  • Verified On: 2026-02-13

Applicability​

  • Tool: all
  • Version Range: unspecified
  • Spec Revision: 2025-11-25

Evidence Sources​

Test Coverage Metadata​

  • Unit tests: true
  • Fixture tests: true
  • E2E tests: false

Examples​

The following examples demonstrate what triggers this rule and how to fix it.

Invalid​

{
  "tools": [{
    "name": "lookup",
    "description": "Looks up records",
    "inputSchema": { "type": "object" },
    "outputSchema": { "type": "invalid_type" }
  }]
}

Valid​

{
  "tools": [{
    "name": "lookup",
    "description": "Looks up records",
    "inputSchema": { "type": "object" },
    "outputSchema": { "type": "object" }
  }]
}