Use completion context only where supported

Completion context was added in MCP 2025-06-18. A completion example spanning an earlier supported version cannot carry that context unchanged. Split the declaration’s scopes when context is needed for only the newer versions.

Requirement

A completion example carries context only from MCP 2025-06-18, where CompleteRequest defines it.

Details

Rule ID: mcp.completion.context.protocol-version
Owner: mcp
Surface: CompleteRequest · Path: context
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
not-applicable	applies	applies	applies	applies

Required by

• MCP Description 0.9.0, Sections 10.4.6 and 11.4
  • 10. Resources and Resource Templates: req-template-completion-context-protocol-version
  • 11. Prompts: req-prompt-completion-context-protocol-version

Based on

• Tier 1 — MCP schema.ts and normative specification text: MCP 2025-03-26 schema.ts, interface CompleteRequest (no context); MCP 2025-06-18 to 2026-07-28 schema.ts, CompleteRequest params context
  • validation/mcp-schemas/2025-03-26/schema.ts#L1092-L1113
  • validation/mcp-schemas/2025-06-18/schema.ts#L1307-L1340
  • validation/mcp-schemas/2025-11-25/schema.ts#L1995-L2025
  • validation/mcp-schemas/2026-07-28/schema.ts#L2582-L2618

Notes

MCP Description does not support completion examples for MCP 2024-11-05 (mcp.completion.protocol-version).

Examples

Invalid example

Source: expected-invalid/invalid-completion-example-semantics.json · Selected: /prompts/1/completionExamples/context-too-early

{
  "argument": {
    "name": "name",
    "value": "a"
  },
  "context": {
    "arguments": {
      "department": "engineering"
    }
  },
  "result": {
    "completion": {
      "values": [
        "Ada"
      ]
    },
    "_meta": {
      "captured": true
    }
  }
}

Rule Source Code

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