Use MCP shapes in interaction requests and responses

Interaction steps carry MCP values: elicitation requests and results, sampling requests, messages, and results, and roots lists. Each has the members its MCP type requires and defines.

Requirement

Elicitation, sampling, and roots requests and responses in interaction steps have the members and member types of their MCP types.

Details

Rule ID: mcp.interaction-message.members
Owner: mcp
Surface: ElicitRequest, ElicitResult, CreateMessageRequest, CreateMessageResult, ListRootsResult, Root
Kind: structural
Requirement level: must
Protocol versions: independent of the MCP protocol version
Document schema locations: #/$defs/elicitationInteractionRequest, #/$defs/elicitationInteractionFormRequest, #/$defs/elicitationInteractionUrlRequest, #/$defs/elicitationInteractionResponse, #/$defs/elicitationInteractionAcceptedResponse, #/$defs/elicitationInteractionDeclinedResponse, #/$defs/samplingCreateMessageRequest, #/$defs/samplingCreateMessageResult, #/$defs/samplingMessage, #/$defs/samplingMessageContent, #/$defs/samplingContentBlock, #/$defs/samplingModelHint, #/$defs/samplingModelPreferences, #/$defs/samplingRequestTool, #/$defs/samplingToolChoice, #/$defs/samplingToolResultContent, #/$defs/samplingToolUseContent, #/$defs/rootsListRequest, #/$defs/rootsListResult, #/$defs/rootDeclaration
Status: internal · Enforcement: internal

Required by

MCP Description 0.9.0, Sections 3.6 and 9.4
- 3. Document Structure: req-carried-defined-fields
- 1. Tools: req-interaction-protocol-version-valid

Based on

Tier 1 — MCP schema.ts and normative specification text: MCP 2025-11-25 and 2026-07-28 schema.ts, CreateMessageRequestParams, SamplingMessage, CreateMessageResult, ElicitRequestFormParams, ElicitResult, ListRootsResult, and Root

Examples

Invalid example

Source: expected-invalid/malformed-sampling-step.json · Selected: /tools/0/interactionExamples/summary/steps/0/request

{
  "messages": [
    {
      "role": "user",
      "content": {
        "type": "text",
        "text": "Summarize the release plan."
      }
    }
  ]
}

Invalid example

Source: expected-invalid/elicitation-response-unknown-member.json · Selected: /tools/0/interactionExamples/approval/steps/0/response

{
  "action": "accept",
  "content": {
    "approved": true
  },
  "unexpected": true
}

Invalid example

Source: expected-invalid/discriminated-union-members.json · Selected: /tools/0/interactionExamples/invalid/steps/0

{
  "type": "elicitation",
  "request": {
    "mode": "url",
    "message": "Authorize",
    "ur": "https://example.test/auth"
  },
  "response": {
    "action": "accepted"
  }
}

Rule Source Code

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