Drop the standalone validate_workflow MCP tool: create_workflow_from_code
already runs the identical parse/validate pipeline, so the pre-flight cost
an extra round trip (the full workflow code was sent twice per build) and
one more tool in every tools/list response.
To keep the validation gate as strong without the pre-flight:
- ParseValidateHandler now exposes fatal validation issues in a separate
`errors` field (still folded into `warnings` for the code-builder agent).
- create_workflow_from_code hard-blocks on fatal validation errors and
returns them all without persisting anything.
- Node-group violations (102_mcp_canvas_groups) are checked before the
save path and reported all at once, instead of first-violation-only.
- MCP instructions, tool descriptions, recovery hints, and scope maps no
longer reference the removed tool.
The in-app code-builder agent's internal validate_workflow tool is
unaffected.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EKFYgNjgLFPkft76sXghep
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