dataclean-mcp

An MCP server that cleans tables deterministically before an AI agent reasons over them. LLMs misread 1.250,50 €, swap day and month in 03/04/2026, choke on NUL bytes and mojibake (Café), and silently drop leading zeros. DataClean fixes these with rules, and it never guesses: an ambiguous value is kept as it was and flagged, and it is converted only when the rest of its column (or a parameter you pass) settles its meaning.

Charging works like this:

• Unreadable input or invalid parameters are refused before any credits are charged.

• A failure after charging is refunded.

What it fixes

• Numbers: 1.250,50 €, $1,250.50, 1 234,5, 1'234.50, (45.30), SAP-style 1.250,50-, 12,5 %, EUR 12. The column decides whether a value like 1,250 uses a thousands or a decimal separator. If nothing in the column decides it, number_locale does, and without either the value is flagged ambiguous_number.

• Dates: ISO, 13/04/2026 (day-first), 04/13/2026 (month-first), 5 de marzo de 2026, March 5, 2026, 5-Mar-26, 3. März 2026, and times with am/pm. 03/04/2026 is converted only when another value in the column, or date_order, settles the order. Dates in the minority order are flagged date_order_conflict.

• Text: removes NUL, control and zero-width characters, turns NBSP into a normal space, repairs mojibake, applies Unicode NFC, and collapses and trims spaces. Null markers (NULL, N/A, #N/A, -, nan…) become empty.

• IDs: digit strings with leading zeros or more than 15 digits (zip codes, card numbers, references) stay text and are never turned into numbers.

• Files: CSV in UTF-8, UTF-16 or Windows-1252, delimiter detected automatically (, ; tab |), title rows above the header skipped, ragged rows padded, duplicate or empty headers renamed. Also reads .xlsx (via base64) and JSON/JSONL.

• Safety: in CSV output, text cells starting with = + - @ get a ' prefix so spreadsheets do not run them as formulas. In .xlsx output they are stored as strings. Schema regexes with nested quantifiers are refused (ReDoS).

Related MCP server: ETL-D MCP Server

Install

1. Buy credits at https://mcp.keyflint.dev to get a license (LIC-...).

2. Add the server to your client:

{
  "mcpServers": {
    "dataclean": {
      "command": "uvx",
      "args": ["dataclean-mcp"],
      "env": { "KEYFLINT_LICENSE": "LIC-..." }
    }
  }
}

Claude Desktop also installs the .mcpb bundle attached to each GitHub release. Hosted mode runs dataclean-mcp --http (or uses the Dockerfile) and reads the license from each request's Authorization: Bearer LIC-... header.

Limits (set by environment variables): DATACLEAN_MAX_BYTES (20 MB), DATACLEAN_MAX_ROWS (200,000), DATACLEAN_MAX_OUTPUT (15 MB). Credit prices can be overridden with DATACLEAN_PRICES=clean_table=2,....

Tests

pip install -e '.[test]'
pytest -q

The tests use a fake KeyFlint gateway and locally signed licenses, so they need no network.

License

Business Source License 1.1. Production use requires a KeyFlint license from the Licensor. On 2030-11-05 the code becomes Apache 2.0.