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Dataset Join & Merge

by Nero-Engine · remote · no sign-in to list tools · v0.1.0 · published by GitHub user Nero-Engine

Join two lists of JSON rows on a key, like SQL or VLOOKUP: left, inner, full, anti joins, union.

Changes · 1
CompareRegistry entry

2 tools: 1 change things and 1 only read.

Scanned Oct 21, 2026

No check matched anything in the tool definitions. No finding is not a safety guarantee. How the checks work.

claude mcp add --transport http dataset-join-merge https://dataset-join-merge.nerolabs.workers.dev/mcp

Tools

Open a tool for its reasons and full description. Descriptions are the publisher's own words, shown as they are.

2 tools

Changes things 1Claude Code: ask
  • join_rowsJoins two lists of JSON rows on a shared key, like a SQL join or a spreadsheet VLOOKUP, and returns the combined rows plus a summary: how many rows matched on each side, match rate…No findings

    Why it is in this group

    • Nothing in its name or description says what it does, so it is counted as a write.
    Description, as the server wrote it
    Joins two lists of JSON rows on a shared key, like a SQL join or a spreadsheet VLOOKUP, and returns the combined rows plus a summary: how many rows matched on each side, match rates, and warnings for duplicate keys, rows missing the key and key fields that exist on no row. Use it to enrich a list with fields from a lookup table (left join), keep only the overlap (inner), combine two sources into one table (full), find rows in one list that are missing from the other (leftAnti or rightAnti), or stack two same-shape lists (union). Keys match case-insensitively with whitespace trimmed by default, and the key can have a different name on each side (email on the left, contact_email on the right). Input and output rows are capped per call; a many-to-many join that would exceed the output cap is refused with the predicted row count, never truncated. Call list_capabilities for the exact limits.
Only reads 1Claude Code: allow
  • list_capabilitiesReturns every join type, key matching mode, conflict strategy and fan-out mode this server supports, the fields it adds to each row, and the input and output row limits per call.No findings

    Why it is in this group

    • The name "list_capabilities" says "list": a word for reading.
    Description, as the server wrote it
    Returns every join type, key matching mode, conflict strategy and fan-out mode this server supports, the fields it adds to each row, and the input and output row limits per call. Free, processes no data.

This is not a safety rating, and no finding is not a safety guarantee. The groups and findings come from fixed checks of the tool definitions the server returned on the date shown, not from its code or what it does when called. How the checks work.

Install

Pinned to version 0.1.0. Values in angle brackets are yours to fill in.

claude mcp add --transport http dataset-join-merge https://dataset-join-merge.nerolabs.workers.dev/mcp

Run in a terminal.

Claude Code permissions

Allow the reads, ask before a change, deny the deletes. Paste into .claude/settings.json.

.claude/settings.json
{
  "permissions": {
    "allow": [
      "mcp__dataset-join-merge__list_capabilities"
    ],
    "ask": [
      "mcp__dataset-join-merge__join_rows"
    ],
    "deny": []
  }
}

Tools that only read are allowed, tools that change things ask first, tools that delete or cancel are denied. It assumes the server is installed as dataset-join-merge. Review it before you use it.