Use sampling tools only where supported

Sampling tools and toolChoice are available from MCP 2025-11-25. Earlier-version interaction examples cannot use those fields. Remove them or narrow the containing Tool’s protocol scope to versions that support them.

Requirement

A sampling request uses tools and toolChoice only from MCP 2025-11-25.

Details

Rule ID: mcp.sampling.tools.protocol-version
Owner: mcp
Surface: CreateMessageRequest · Path: tools, toolChoice
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 9.4
  • 9. Tools: req-interaction-sampling-protocol-version

Based on

• Tier 1 — MCP schema.ts and normative specification text: MCP 2025-06-18 schema.ts, CreateMessageRequest (no tools); MCP 2025-11-25 and 2026-07-28 schema.ts, CreateMessageRequestParams tools and toolChoice
  • validation/mcp-schemas/2025-06-18/schema.ts#L1028-L1065
  • validation/mcp-schemas/2025-11-25/schema.ts#L1573-L1622
  • validation/mcp-schemas/2026-07-28/schema.ts#L2086-L2152

Examples

Invalid example

Source: expected-invalid/invalid-tool-interaction-example-semantics.json · Selected: /tools/0/interactionExamples/broken/steps/2/request

{
  "messages": [
    {
      "role": "user",
      "content": {
        "type": "text",
        "text": "Summarize the release plan."
      }
    }
  ],
  "tools": [
    {
      "name": "diff_summary",
      "inputSchema": {
        "type": "object"
      }
    }
  ],
  "maxTokens": 120
}

Rule Source Code

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