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    Works with the AI tools you already use

    Claude CodeClaude CodeCursorCursorCodex CLICodex CLIGitHub CopilotGitHub CopilotGemini CLIGemini CLI+20 more

    n8n Expression & Mapping Debugger

    1

    Diagnose and fix n8n expression errors, JSON mapping failures, and broken item linking.

    $8.99

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    n8n Expression & Mapping Debugger

    n8n Expression & Mapping Debugger

    Example session with this skill installed

    My n8n Code node runs once for all items and uses:

    return $input.all().map(item => ({
  json: {
    email: item.json.email.toLowerCase()
  }
}));

    Downstream, {{ $("Webhook").item.json.id }} fails because n8n cannot determine the matching item. Keep one output per input and fix the Code node.

    • Read your context and instructions
    • Compiled the n8n expression

    Cause

    The Code node creates new output items without preserving which input item produced each output. This breaks the item lineage required by {{ $("Webhook").item.json.id }}.

    Corrected code

    return $input.all().map((item, index) => ({
  json: {
    email: item.json.email.toLowerCase()
  },
  pairedItem: {
    item: index
  }
}));

    Why it works

    Each output item is explicitly linked to the input item at the same index. This allows downstream .item references to resolve the corresponding upstream Webhook item.

    Verify

    1. Run the Code node with several input items.
    2. Confirm that input and output item counts match.
    3. Preview {{ $("Webhook").item.json.id }} downstream.
    4. Confirm that each output resolves to the ID of its corresponding Webhook item.

    This assumes that every output corresponds to the input item at the same index and that the earlier lineage back to Webhook is still intact.

    Confidence: High.

    Connects securely to your tools. The creator never sees your data.

    What you get

    Fix broken item linking and pairedItem errors in Code nodes.Resolve path shape errors for nested JSON structures.Correct cardinality issues between single items and arrays.Debug [object Object] output in text fields.

    About this skill

    Stop guessing why an n8n field is blank, returns undefined, resolves to the wrong item, or produces [object Object].

    n8n Expression & Mapping Debugger is a focused Agent Skill for diagnosing expression and data-mapping failures inside n8n.

    It helps with: • nested JSON paths and arrays • $json and previous-node references • .item, .first() and .all() • Merge and Aggregate item-linking problems • Code-node pairedItem lineage • null and undefined values • object-to-text mapping errors

    Give it the failing expression, relevant Input/Output JSON, actual result and expected value. It identifies the smallest proven cause and returns a corrected expression or mapping change, explanation and verification steps.

    The Skill is evidence-first: it does not invent JSON paths, node names or item relationships when the available data is insufficient.

    Best for n8n builders, automation freelancers, agencies and operations teams.

    Scope: n8n expressions and data mapping only. It does not troubleshoot credentials, installation, infrastructure or complete workflow architecture.

    How to install

    Works the same in every agent - Claude, Cursor, Codex, Copilot and 20+ more.

    ~30 seconds
    1. 1

      Download the ZIP

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    2. 2

      Unzip into your skills folder

      Every agent reads skills from one folder on your machine. Drop the unzipped folder in there.

    3. 3

      Ask your agent to use it

      Restart the agent if it was already running. It picks the skill up automatically - no config needed.

    Skills folder by agent

    Click the path to copy it. Create the folder if it does not exist yet.

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    Security scanned

    Passed our 8-point scan before listing

    Fresh listing

    Recently published to Agensi

    30-day refund

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    Trust & safety

    Security scanned

    Verified clean 8 days ago

    • Passed all security checks, Safe to install

    Listed8 days ago
    Updated5 days ago

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