Draft: fix(mcp): wrap non-object outputs as valid structuredContent

James Hebdenrequested to merge
jhebden/mcp-structured-content-fix into main

Summary

Strict MCP clients (notably Claude Desktop) reject structuredContent that isn't a JSON object, breaking glab mr list --output json and glab issue list --output json when called via the MCP tool surface. This MR adds an ensureStructuredRecord wrapper around non-object payloads before they land in CallToolResult.StructuredContent:

  • Object → passthrough.
  • Array → {"data": [...]}.
  • Scalar / nil → {"value": ...}.

The accompanying TextContent block still carries the raw payload unchanged, so existing clients that read the textual content see no difference.

Fixes #8302 (closed).

Context

This is the first MR in a 6-MR stack split out from the closed MR !3154. That MR did too much; this stack lands each piece independently. See the bug report at #8302 (closed) for the SDK contract citation and the strict-client repro.

Test plan

  • go test ./internal/commands/mcp/serve/... passes — covers ensureStructuredRecord for object passthrough, array wrap, scalar wrap, and nil.
  • Manually invoke glab mr list --output json via Claude Desktop's MCP client and confirm the response is accepted (was previously rejected as expected record / invalid_type).
  • No change to the CLI's JSON output shape — glab mr list --output json still emits a top-level array on stdout.

Merge request reports