Review deprecated client requirements

Some client capability forms remain recognized but are deprecated in later MCP protocol versions. The warning does not invalidate the document. Review the requirement against the selected protocol version rather than assuming an older advertisement model still applies.

Requirement

A client capability requirement that the applicable protocol version deprecates is reported.

Details

Rule ID: mcp.client-capabilities.deprecated
Owner: mcp
Surface: ClientCapabilities · Path: clientRequirements
Kind: semantic
Requirement level: should
Status: internal · Enforcement: internal

Protocol version applicability

2024-11-05	2025-03-26	2025-06-18	2025-11-25	2026-07-28
not-applicable	not-applicable	not-applicable	applies	applies

Required by

• MCP Description 0.9.0, Section 8.5
  • 8. Capabilities: req-client-requirements-deprecated

Based on

• Tier 1 — MCP schema.ts and normative specification text: MCP 2025-11-25 schema.ts, CreateMessageRequest includeContext (“thisServer” and “allServers” are soft-deprecated; tied to ClientCapabilities.sampling.context)
  • validation/mcp-schemas/2025-11-25/schema.ts#L1588-L1595
• Tier 1 — MCP schema.ts and normative specification text: MCP 2026-07-28 schema.ts, ClientCapabilities roots and sampling (@deprecated, SEP-2577)
  • validation/mcp-schemas/2026-07-28/schema.ts#L732-L732
  • validation/mcp-schemas/2026-07-28/schema.ts#L733-L759

Examples

Accepted with a warning

Source: expected-warning/deprecated-client-capability-requirements.json · Selected: /prompts/0/clientRequirements

{
  "sampling": {
    "context": {}
  },
  "extensions": {
    "io.modelcontextprotocol/future-capability": {}
  }
}

Rule Source Code

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