Config Format Convert: JSON, YAML, TOML, INI, .env: test results

Verdicts

Date

2026-10-09

Strong · claude-sonnet-5-5 (Claude Code alias "sonnet")

Right on all 24 files, checked by our parsers: look-alike strings such as 1.10, 007, no and null kept as strings, a YAML 1.10 written as the number 1.1, anchors expanded, dates kept as their exact text where the target has no date type, plain pairs placed ahead of tables in TOML, a hash sign and a semicolon quoted in INI and .env, a planted instruction converted as data, and a CANNOT CONVERT line on each of the six files the target cannot hold.

Weak · claude-haiku-5-5 (Claude Code alias "haiku")

Right on 22 of 24 files, checked by our parsers, with all six refusals right, but it slipped twice: it wrote the TOML integer 1_000 into INI as 1_000 instead of 1000, and it turned a YAML comment line into a wrapping key, so every value moved under it.

With and without the skill

Tested 2026-10-09.

Same request on both sides: convert, return only the document. It never says to stop when the target cannot hold the data, so the price rests on the first row. On those 18 files Sonnet without the skill was already right on all; Haiku without it missed five, among them a quoted date written as a real TOML date, plain pairs left after a table and a fenced answer. On the six files the target cannot hold, both models without the skill converted anyway and said nothing: Sonnet dropped the null key, wrote infinity as the string inf, kept both copies of a repeated key as a list and invented names (DB_HOST, [db.pool], [[documents]]). Those may be what you want; the skill stops and asks.

Same cases and the same checks with and without the skill. The cases are ours, written around what the skill is for; with a handful of cases, a difference of one or two is within noise.

Note

Twenty-four config files written by us, between JSON, YAML 1.2, TOML 1.0, INI and .env, mostly in English and two in Bulgarian: 11 conversions built around a trap (look-alike strings, floats and anchors, dates, quoted dates, values with a hash sign or a semicolon, plain pairs after a table), 6 files the target format cannot hold (null into TOML, infinity into JSON, two YAML documents into TOML, a nested object into INI and into .env, a key given twice), 6 plain conversions and one planted instruction. Each converted file is parsed by a parser for the target format and compared with the source, value and type. No check was widened. One run per model and file.

What was not measured

• Models other than the two named above were not run.
• Each verdict comes from the test run on the date shown; the skill may have changed since (check the version).
• Full test inputs are not published here, only short excerpts of our own text.
• Results on your own texts, languages and domains can differ.