About Csstruth
Csstruth is an MCP server in the Browser category: hard ground truth for CSS — the browser's rendered layout as deterministic, diffable text for coding agents. MCP server + CLI.
Install
From source
git clone https://github.com/ikraamg/csstruthThis server has no ConduID identity, so agent calls to it are not receipted. Pin the version you install and review the source before granting it credentials.
Tools (12)
baselineSnapshot the CURRENT violation set as a sorted, diff-friendly file — the fix for adopting `check`/`verify` on a page that isn't (and may not soon be) fully clean. Pass the resulting file to `check`/`verify`'s `--baseline` to report only NEW/RESOLVED violations instead of an all-or-nothing PASS/FAIL. See **Adopting on a brownfield page** below.
Parameters not published.
blame**"Which commit broke this?"** — walks a git repo's history backwards (newest→oldest, capped at 25 commits by default) checking out each commit into a scratch `git worktree`, until it finds the first commit where the current violation is gone. Names the culprit (`file:line`-style: sha, subject, date, author) plus the layout delta and violations it introduced. STATIC roots only in v1 (no dev-server/build step per checkout); the user's HEAD/index/working tree are never touched.
Parameters not published.
checkLayout-bug scan: viewport overflow, visible parent bleed, clipped text, unintended overlap, zero-size/tiny tap targets — exact px + the suspect rule at `file:line`.
Parameters not published.
diffStructural diff vs a snapshot: what moved/resized/appeared/disappeared, in px.
Parameters not published.
explainTrace any property to its source: which declaration wins (`file:line`, source-mapped), which lost and why, and what layout constraint overrides the declared value (flex-basis, min/max, grid).
Parameters not published.
fixPropose (default) or **apply** mechanical patches for fixable violations (clipped text, tiny tap targets, a fixed px width bleeding/overflowing). DRY-RUN unless `--apply`; writes are confined to `--root` and guarded by a stale-source check. See **Safety** below.
Parameters not published.
inspectOne element in depth: box model, non-default styles, stacking context, why it has its width/height.
Parameters not published.
layoutThe LayoutTree of the rendered page (scope with `selector`/`depth`; auto-budgeted on huge pages).
Parameters not published.
snapshotLock the current layout to a named `.tree` file (per-viewport with `--viewports`).
Parameters not published.
stabilityLoad-time layout-shift report (Cumulative Layout Shift): what moved, when, and by how much, plus unsized `img`/`video` suspects. Timing-dependent (an observation, not a deterministic snapshot). Score is the raw sum over the observation window; the CWV metric uses session windows — multi-burst pages may score higher here. Scoped to the top frame — shifts inside an iframe aren't observed.
Parameters not published.
verify**"Is this OK?"** — one call: invariants across a viewport sweep (default 375/768/1280) + optional snapshot diffs. First line is always `VERDICT: PASS` or `VERDICT: FAIL (…)`.
Parameters not published.
watch**Live diff stream while you edit.** Holds one page open, polling the layout signature every `--interval` ms (default 500); on a change, prints the layout delta and any NEW/RESOLVED violations under a `[HH:MM:SS]` block — silent otherwise. Survives an HMR full-refresh (`page reloaded`, same URL); stops if you navigate elsewhere or the dev server dies. Ctrl+C for a clean exit. CLI only — see **Use `watch` from a background shell** below.
Parameters not published.
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