fix(mcp): fix caret misalignment and tool schema contract validation by waleedlatif1 · Pull Request #5566 · simstudioai/sim

waleedlatif1 · 2026-07-10T19:14:43Z

Summary

Fix MCP server form modal caret drifting from typed text in the Server URL and Header fields (font-weight mismatch between the ghost input and its formatted overlay)
Fix "Response failed contract validation" crash on the MCP tools page when a real MCP server returns a tool schema with array-form items (tuple validation) or non-primitive enum values — the contract's property schema was stricter than valid JSON Schema

Type of Change

Bug fix

Testing

Tested manually

Checklist

Code follows project style guidelines
Self-reviewed my changes
Tests added/updated and passing
No new warnings introduced
I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

The Server URL and Header fields render a transparent input under a formatted overlay div for env-var highlighting. The overlay used font-medium/font-sans but the real input didn't, so glyph widths diverged and the native caret drifted from the visible text as you typed.

discoverMcpToolsContract's property schema rejected legal JSON Schema that real MCP servers can return: array-form `items` (tuple validation) and non-primitive `enum` values. Any server exercising either shape failed contract validation client-side and blanked the entire MCP tools list.

vercel · 2026-07-10T19:14:48Z

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cursor · 2026-07-10T19:14:53Z

PR Summary

Low Risk
UI typography fix and looser schema validation plus safer parameter editing; no auth, persistence, or execution-path changes.

Overview
Fixes caret drift in the MCP server form URL/header fields by giving the transparent ChipInput the same font-medium font-sans styling as the formatted overlay, so typed text and the caret line up with the visible env-var highlighting.

Stops “Response failed contract validation” on MCP tool discovery when servers return valid but richer JSON Schema: Zod/types now allow items as a single schema or an array (tuple form) and enum members as arbitrary JSON values, not only primitives.

In workflow MCP tool args, non-primitive enum values no longer use the dropdown (which would show [object Object]); they use the long JSON editor instead, with stringify/parse so object/array parameters and complex enums store real JSON values.

^{Reviewed by Cursor Bugbot for commit a6d48f8. Configure here.}

greptile-apps · 2026-07-10T19:16:17Z

Greptile Summary

This PR fixes MCP form input rendering and broadens MCP tool schema handling.

Aligns the MCP server form caret with formatted overlay text.
Accepts tuple-style array items in MCP tool schemas.
Accepts arbitrary JSON values in MCP schema enum entries.
Routes non-primitive enum and JSON-shaped arguments through the long JSON editor.

Confidence Score: 5/5

This looks safe to merge.

No blocking issues found in the changed code.

Important Files Changed

Filename	Overview
apps/sim/app/workspace/[workspaceId]/settings/components/mcp/components/mcp-server-form-modal/mcp-server-form-modal.tsx	Aligns the transparent input font with the formatted overlay used in the MCP server form.
apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/panel/components/editor/components/sub-block/components/mcp-dynamic-args/mcp-dynamic-args.tsx	Adds enum shape detection and parses JSON-backed long-input values before storing them.
apps/sim/lib/api/contracts/mcp.ts	Widens MCP tool property validation for tuple `items` and arbitrary JSON enum members.
apps/sim/lib/mcp/types.ts	Updates MCP schema property types to match the widened API contract.

_{Reviews (5): Last reviewed commit: "fix(mcp): parse JSON-typed long-input ed..." | Re-trigger Greptile}

The MCP dynamic-args dropdown stringifies enum members for its labels/values. Now that the tool schema contract accepts non-primitive enum members (object/array), routing those through the dropdown would collapse distinct values to "[object Object]" and submit that string as the tool argument. Gate the dropdown on primitive-only enums; non-primitive enums fall through to the existing type-based branching (the JSON long-input editor for object/array types), which round-trips arbitrary JSON correctly.

waleedlatif1 · 2026-07-10T19:21:41Z

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waleedlatif1 · 2026-07-10T19:21:43Z

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^{Reviewed by Cursor Bugbot for commit 54f7326. Configure here.}

…type isPrimitiveEnum() correctly excluded object/array enum members from the dropdown, but the fallback only reached the long-input JSON editor when paramSchema.type was 'array'. An object-typed (or untyped) param with a non-primitive enum fell through to the default short-input, which stringifies via toString() and drops the enum-membership guarantee entirely. Any non-primitive enum now routes straight to long-input, independent of the declared type.

waleedlatif1 · 2026-07-10T19:25:18Z

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waleedlatif1 · 2026-07-10T19:25:20Z

@cursor review

…nput editor The long-input JSON editor received value={value || ''} unconditionally, so an argument already holding a parsed object/array (loaded from the block's JSON arguments field) rendered as "[object Object]" or a comma-joined list instead of valid JSON, and saving would overwrite the real value with that mangled text. Serialize non-string values with JSON.stringify before display; onChange still stores the raw text the user edits, unchanged.

waleedlatif1 · 2026-07-10T19:34:55Z

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waleedlatif1 · 2026-07-10T19:34:57Z

@cursor review

cursor

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^{Reviewed by Cursor Bugbot for commit 8822d45. Configure here.}

The long-input editor's onChange always stored the raw typed text, so a param whose schema requires an object/array/non-primitive-enum value (e.g. entering {"mode":"strict"}) was persisted as a string, not the actual JSON value — the MCP tool call could receive the wrong type. requiresJsonValue() identifies these schemas; onChange now parses the edited text back into the real value once it's valid JSON, falling back to the raw string mid-edit so the controlled textarea keeps reflecting in-progress keystrokes.

waleedlatif1 · 2026-07-10T19:42:44Z

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waleedlatif1 · 2026-07-10T19:42:46Z

@cursor review

cursor

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Comment @cursor review or bugbot run to trigger another review on this PR

^{Reviewed by Cursor Bugbot for commit a6d48f8. Configure here.}

waleedlatif1 added 2 commits July 10, 2026 12:14

greptile-apps Bot reviewed Jul 10, 2026

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Comment thread apps/sim/lib/api/contracts/mcp.ts

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Comment thread ...anel/components/editor/components/sub-block/components/mcp-dynamic-args/mcp-dynamic-args.tsx

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Comment thread ...anel/components/editor/components/sub-block/components/mcp-dynamic-args/mcp-dynamic-args.tsx

chore(mcp): fold inline comment into the existing TSDoc block

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Comment thread ...anel/components/editor/components/sub-block/components/mcp-dynamic-args/mcp-dynamic-args.tsx Outdated

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waleedlatif1 merged commit f0d85cb into staging Jul 10, 2026
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waleedlatif1 deleted the worktree-fix-mcp-modal-caret branch July 10, 2026 19:54

waleedlatif1 mentioned this pull request Jul 10, 2026

v0.7.29: GLM, ui and ux improvements #5567

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waleedlatif1 commented Jul 10, 2026

Summary

Type of Change

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Confidence Score: 5/5

Important Files Changed

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