DataClean

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).

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,....

Visual cards (MCP Apps)

In Claude, ChatGPT, VS Code and Goose every paid tool and credits_balance renders as an interactive card in the chat: credit balance with a refill bar and a buy button, or a result summary (key figures, issues, table preview and credits charged). It is the ui://dataclean/card.html resource, self-contained with no network access. Other clients keep getting the same JSON as before.

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.