Server config templates should include required type field for clients like Claude Code #3233

Summary

I maintain an MCP server (wan-ip-check, see github.com/AC13139/wan-ip-check). When integrating with Claude Code, I discovered that the project-scoped `.mcp.json` example templates shown in the official Go/Python/TypeScript SDK READMEs omit the `"type": "http"` field — Claude Code then silently refuses to connect with:

[Warning] [wan-ip-check] mcpServers.wan-ip-check: Skipped — MCP server "wan-ip-check" has a "url" but no "type"; add "type": "http" (or "sse" / "ws") to this entry

This is because Claude Code's loader requires both `type` AND `url` to be explicit on every server entry. `transport` (the spec field) is NOT inferred as a substitute for `type` (the client field).

What I'd like

1. A canonical field-matrix table in the MCP server config docs covering at minimum:
   • `type` (required by some clients): http, sse, ws (for URL-based) and stdio (uses command+args)
   • `url`: required when type is http/sse/ws
   • `transport` (MCP 2026-07-28 spec name for the streamable HTTP variant): how it relates to `type`
2. Updated example templates across the SDK READMEs to include `"type": "http"` for HTTP-streamable servers.
3. A note in the spec explaining that `type` is client-defined (varies by host) and `transport` is the spec-defined field for transport negotiation.

Why I'm filing here, not in a SDK repo

The spec / docs page is the canonical source of truth for config schema. SDKs copy from it. Updating it once propagates everywhere.

References

• Companion issue on Claude Code itself: MCP config: misleading error when server is missing type field; transport not inferred as substitute anthropics/claude-code#86143
• Reproducer config: `{ "mcpServers": { "x": { "url": "...", "transport": "streamable-http", "headers": {...} } } }` — silently skipped by Claude Code without `type`.
• Working config: add `"type": "http"` next to `url`.

Thanks for the great spec, by the way — the 2026-07-28 changes around `structuredContent` and `isError` are working great on our end.