formatting-insight-axes
Pick the right y-axis unit when creating or updating an insight via posthog:insight-create or posthog:insight-update — both TrendsQuery (trendsFilter.aggregationAxisFormat) and SQL insights (DataVisualizationNode, chartSettings.yAxis[].settings.formatting). Use when the agent is about to add a formula purely to convert units (e.g. dividing seconds by 60 to display minutes), when a mathproperty or SQL column is a duration, currency, ratio, or large count, or whenever the user mentions "format the y-axis", "duration", "seconds", "minutes", "hours", "milliseconds", "ms", "percentage", "%%", "currency", "decimals", "axis label", or "axis unit" in the context of a graph insight.
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/posthog/ai-plugin --skill formatting-insight-axes- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads formatting-insight-axes automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
SKILL.md
The instructions your agent reads when the skill is triggered.
Formatting insight axes
PostHog renders insights with a built-in axis formatter. Use it instead of contorting the query or a literal prefix/postfix to fake units.
The two insight kinds configure it in different places:
- TrendsQuery —
trendsFilter.aggregationAxisFormat(this page, below) - SQL insights (
DataVisualizationNode) — per-columnsettings.formatting(see SQL insights)
The anti-pattern
If you are reaching for any of these, stop and pick a format below first:
formula: "A / 60"withaggregationAxisPostfix: " mins"— manual seconds -> minutesformula: "A / 1000"withaggregationAxisPostfix: " s"— manual ms -> secondsformula: "A * 100"withaggregationAxisPostfix: "%"— manual ratio -> percentaggregationAxisPostfix: "ms"/"s"/"min"/"hr"on raw values
These freeze the unit at one scale. The built-in formatter picks a friendly unit per value (1.5s, 2m 12s, 1h 4m) and keeps the underlying series numerically correct for further math, breakdowns, and alerts.
Available formats
Set trendsFilter.aggregationAxisFormat on the TrendsQuery:
| Value | Use when the series is... | Renders as |
|---|---|---|
numeric (default) | a plain count | 1,234 |
duration | seconds (any scale) | 45s, 2m 12s, 1h 4m |
duration_ms | milliseconds | 850ms, 1.5s, 1m 4s |
percentage | already 0-100 | 47.3% |
percentage_scaled | a ratio 0-1 | 47.3% |
currency | money in the project's base currency | $1,234.56 (or local code) |
short | large counts you want compacted | 1.2K, 3.4M |
Companion fields on trendsFilter:
aggregationAxisPrefix— literal prefix (e.g."$") when you need a symbol pinned to a specific currency or unit, regardless of project settingsaggregationAxisPostfix— literal suffix; reserve for genuine units the format can't express (e.g." req"," events"), never for"mins"/"s"/"%"— the percentage formats already append the%sign, so a"%"postfix renders50%%decimalPlaces— cap decimals (1 or 2 is usually right for currency / ratios)
Currency — pick format or prefix carefully
aggregationAxisFormat: "currency" renders with the project's base currency
(set in project settings, defaults to USD). Use it when the underlying values
are in that same currency — e.g. revenue events that PostHog auto-converts to
the project's base currency.
If the values are pinned to a specific currency regardless of project (e.g.
$ai_total_cost_usd is always USD, even on a EUR-base project), use
aggregationAxisPrefix: "$" + decimalPlaces: 2 so the symbol matches the
data. Using format: "currency" here would render USD values with € on a
EUR project.
When the series is in seconds
If the series is in seconds (latency, session length, time-to-first-event,
processing time, page load, etc.), silently default to
aggregationAxisFormat: "duration". Do not stop to ask — the formatter is
non-destructive (the underlying values stay in seconds either way, only the
labels change), so picking it is always at least as good as raw seconds.
Only confirm with the user when they have explicitly named a fixed unit they want pinned ("show this in minutes", "graph the average in hours"):
"I can pin the y-axis to minutes by dividing the series by 60, or use PostHog's
durationformatter which auto-picks seconds / minutes / hours per value —90srenders as1m 30sand5400sas1h 30m. Which would you prefer?"
In one-shot MCP contexts where no user is in the loop, just pick duration
and move on.
Examples
Latency — duration in milliseconds
{
"kind": "TrendsQuery",
"series": [
{
"kind": "EventsNode",
"event": "$pageview",
"math": "p95",
"math_property": "$performance_page_loaded"
}
],
"trendsFilter": {
"aggregationAxisFormat": "duration_ms"
}
}
Average session length — duration in seconds
{
"kind": "TrendsQuery",
"series": [
{
"kind": "EventsNode",
"event": "$pageleave",
"math": "avg",
"math_property": "$session_duration"
}
],
"trendsFilter": {
"aggregationAxisFormat": "duration"
}
}
Revenue — currency in the project's base currency
{
"trendsFilter": {
"aggregationAxisFormat": "currency",
"decimalPlaces": 2
}
}
Fixed-currency value (e.g. LLM cost in USD) — pin the symbol
{
"trendsFilter": {
"aggregationAxisPrefix": "$",
"decimalPlaces": 2
}
}
Conversion rate — percentage from a 0-1 formula
{
"kind": "TrendsQuery",
"series": [
{
"kind": "EventsNode",
"event": "checkout_completed",
"math": "dau"
},
{
"kind": "EventsNode",
"event": "checkout_started",
"math": "dau"
}
],
"trendsFilter": {
"formula": "A / B",
"aggregationAxisFormat": "percentage_scaled",
"decimalPlaces": 1
}
}
SQL insights (DataVisualizationNode)
SQL insights have no trendsFilter.
Formatting is per column, on chartSettings.yAxis[].settings.formatting for a chart and top-level tableSettings.columns[].settings.formatting for a table.
{
"kind": "DataVisualizationNode",
"source": { "kind": "HogQLQuery", "query": "SELECT week, conversion_rate FROM ..." },
"display": "ActionsLineGraph",
"chartSettings": {
"xAxis": { "column": "week" },
"yAxis": [
{
"column": "conversion_rate",
"settings": { "formatting": { "style": "percent", "decimalPlaces": 1 } }
}
]
}
}
style is none, number, short, or percent — no duration or currency.
Express those with prefix / suffix, or in the SQL itself.
percent both appends the % sign and multiplies the value by 100 (like the trends percentage_scaled format; there is no unscaled variant).
So feed it a 0-1 ratio and leave suffix unset — pick one shape, never a mix:
| SQL returns | formatting | Renders |
|---|---|---|
a 0-1 ratio (a / b) | {"style": "percent", "decimalPlaces": 1} | 47.3% |
0-100 (round(100.0 * a / b, 1)) | {"style": "number", "suffix": "%", "decimalPlaces": 1} | 47.3% |
A mix renders broken: style: "percent" plus a "%" suffix gives 47.3%%, and percent on an already-scaled 0-100 column gives 4730%.
Prefer the ratio form — it keeps the 100.0 * out of the query, so the stored column stays a plain ratio for anything else that reads it.
Updating an existing insight
If an insight you are already editing uses one of these anti-patterns — a
trends formula/postfix pair, or a SQL column with both style: "percent"
and a "%" suffix — fix it in the same posthog:insight-update call: drop the
divide-by-N or 100.0 * and the literal %, and let the format own the unit.
Values stay the same, only labels change. Do not scan unrelated insights — fix
only the ones you are already touching.
FAQ
What does the formatting-insight-axes skill do?
Pick the right y-axis unit when creating or updating an insight via posthog:insight-create or posthog:insight-update — both TrendsQuery (trendsFilter.aggregationAxisFormat) and SQL insights (DataVisualizationNode, chartSettings.yAxis[].settings.formatting). Use when the agent is about to add a formula purely to convert units (e.g. dividing seconds by 60 to display minutes), when a mathproperty or SQL column is a duration, currency, ratio, or large count, or whenever the user mentions "format the y-axis", "duration", "seconds", "minutes", "hours", "milliseconds", "ms", "percentage", "%%", "currency", "decimals", "axis label", or "axis unit" in the context of a graph insight.
How do I install formatting-insight-axes?
Run npx skills add https://github.com/posthog/ai-plugin --skill formatting-insight-axes in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/formatting-insight-axes/ (personal) or .claude/skills/formatting-insight-axes/ (project).
Which AI agents can use formatting-insight-axes?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is formatting-insight-axes safe to install?
No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.
Who maintains formatting-insight-axes?
It is published by posthog in posthog/ai-plugin, and it is an official skill from the maker of the technology it covers. It has 181 recorded installs.
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