Suomi Finnish Skill

Finnish language skill for Claude, Codex and any other AI that supports skills

**Teach AI to write correct Finnish.** This skill provides comprehensive Finnish language rules — spelling, grammar, punctuation, compound words, and style — so AI produces natural, publication-ready Finnish instead of the awkward, anglicism-filled output LLMs typically generate.

Works with Claude Code, Codex, and any other AI agent platform that supports skills.

Built on the official [Kielitoimiston ohjepankki](https://kielitoimistonohjepankki.fi/) (Institute for the Languages of Finland).

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Why this exists

LLMs make predictable mistakes when writing Finnish:

• Compound words split apart: "verkko sivusto" instead of verkkosivu, "asiakas palvelu" instead of asiakaspalvelu
• Anglicisms everywhere: "sukella syvemmalle", "implementoida", "adressoida"
• Wrong punctuation: English-style decimals (3.14 instead of 3,14), Oxford commas, missing commas before subordinate clauses
• Overly pompous tone: American corporate rhetoric translated literally into Finnish
• Capitalization errors: weekdays, months, and nationalities capitalized (English rules applied to Finnish)
• Broken inflection: Finnish has 15 grammatical cases and complex word inflection — LLMs frequently produce wrong case endings, garbled possessive suffixes, and incorrect verb conjugations
• Mangled ä and ö: LLMs drop or swap Finnish diacritics, writing "a" instead of "ä" and "o" instead of "ö", which changes word meanings entirely and leads to incorrect translations

This skill catches and prevents all of these. It's been used in production to generate hundreds of pages of Finnish web content.

Installation

Option 1: Add to a project (recommended)

Copy the `SKILL.md` file into your project's Claude Code skills directory:

# Create the skills directory if it doesn't exist
mkdir -p .claude/skills

# Copy the skill
cp SKILL.md .claude/skills/suomi-finnish.md

The skill