Check Tool examples against their schemas

Example input must satisfy the resolved inputSchema, and successful structured output must satisfy outputSchema when supplied. Correct the example or the declaration’s schema. Where resolution or dialect support prevents complete checking, the diagnostic must make that limitation visible.

Requirement

A Tool example input validates against inputSchema, and its structuredContent against outputSchema, for every applicable protocol version; incomplete validation is reported.

Details

Rule ID: mcpdesc.tool.example.schema-conformance
Owner: mcpdesc
Surface: Tool example · Path: examples, interactionExamples
Kind: mcpdesc-semantic
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, Sections 9.2, 9.3, and 9.4
  • 9. Tools: req-tool-example-input-valid
  • 9. Tools: req-tool-example-incomplete-validation

Based on

• Tier 1 — MCP schema.ts and normative specification text: MCP 2025-06-18 to 2026-07-28 specification, Server Features, Tools, Output Schema (structured results conform to outputSchema)
  • https://github.com/modelcontextprotocol/modelcontextprotocol/blob/dae694f61a31f7a3ec2af3aff709e11f70f61e48/docs/specification/2025-06-18/server/tools.mdx#L309-L382
  • https://github.com/modelcontextprotocol/modelcontextprotocol/blob/dae694f61a31f7a3ec2af3aff709e11f70f61e48/docs/specification/2025-11-25/server/tools.mdx#L335-L408
  • https://github.com/modelcontextprotocol/modelcontextprotocol/blob/dae694f61a31f7a3ec2af3aff709e11f70f61e48/docs/specification/2026-07-28/server/tools.mdx#L509-L631

Notes

Before MCP 2025-11-25 no embedded dialect is defined, so only the legacy shape is checked and the warning reports the gap.

Examples

Accepted with a warning

Source: expected-warning/pre-dialect-tool-example.json · Selected: /tools/0/examples/friendly

{
  "input": {
    "name": "Example User"
  },
  "result": {
    "content": [
      {
        "type": "text",
        "text": "Hello, Example User."
      }
    ]
  }
}

Accepted with a warning

Source: expected-warning/unresolved-external-tool-example-ref.json · Selected: /tools/0/examples/external-identifier

{
  "input": {
    "identifier": "example-123"
  },
  "result": {
    "resultType": "complete",
    "content": [
      {
        "type": "text",
        "text": "Found example-123."
      }
    ]
  }
}

Invalid example

Source: expected-invalid/tool-example-schema-mismatches.json · Selected: /tools/0/examples/wrong-types

{
  "input": {
    "count": "one"
  },
  "result": {
    "resultType": "complete",
    "content": [
      {
        "type": "text",
        "text": "one"
      }
    ],
    "structuredContent": {
      "total": "one"
    }
  }
}

Invalid example

Source: expected-invalid/component-contextual-examples.json · Selected: /components/toolExamples/bad-input

{
  "input": {
    "query": 42
  },
  "result": {
    "resultType": "complete",
    "content": [],
    "structuredContent": {
      "count": "one"
    }
  }
}

Rule Source Code

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