feat(mcp): expose chart display + formatting settings on insight tools#60868
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The agent-facing `AssistantDataVisualization*` schema that the MCP `insight-create` / `insight-update` tools validate against only exposed `yAxisPosition` under a series' display settings, even though the backend `DataVisualizationNode` accepts the full `ChartSettingsDisplay`. Agents could not toggle a trend line (or set most display options) on a SQL insight without the strict Zod layer rejecting the field before it reached Django. Enrich the agent schema to match what the backend already supports: - per-series display: `trendLine`, `displayType` (mix line/bar/area), `label`, `color` (in addition to `yAxisPosition`) - per-series/axis number `formatting`: `prefix`, `suffix`, `style`, `decimalPlaces` - chart-level `showValuesOnSeries` Each field carries a docstring so the generated MCP tool schema documents valid options for agents. Regenerated schema.json, schema.py, the MCP tool Zod, and the tool-schema snapshots. Generated-By: PostHog Code Task-Id: 563610e9-d6a9-45ef-962e-8b92a573cca6
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Purely additive, optional schema fields for the LLM analytics assistant. The DisplayType and Style enum moves in schema.py are a clean consolidation (moved up to be shared), all new fields default to None, and all six files (Python schema, TS types, JSON schema, MCP Zod tool, and two test snapshots) are kept consistent with each other.
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Document the per-series display settings (displayType, trendLine, label, color, yAxisPosition), number formatting (prefix, suffix, style, decimalPlaces), and chart-level showValuesOnSeries that are now available on the insight-create and insight-update MCP tools for SQL-backed insights. Ref: PostHog/posthog#60868
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Problem
Updating the display settings of a SQL-backed (DataVisualization) insight through the PostHog MCP was unnecessarily hard. The agent-facing
AssistantDataVisualization*schema — which theinsight-createandinsight-updatetools validate against — only exposedyAxisPositionunder a series' display settings, even though the backendDataVisualizationNodealready accepts the fullChartSettingsDisplay(trendLine,displayType,label,color, …) plus per-series number formatting.Because the strict Zod layer used
additionalProperties: false, an agent trying to turn on a trend line had every reason to expect the field to be stripped or rejected before the request reached Django. The change happened to pass, but only by sending an undocumented field — agents had to hedge and verify rather than trust the schema.Changes
Enriched the agent-facing DataVisualization insight schema (
schema-assistant-queries.ts) to surface the display settings the backend already supports, so they flow throughinsight-create/insight-updatewith documented, validated fields:trendLine,displayType(auto/line/bar/area, to mix series types),label,color— alongside the existingyAxisPosition.formattingblock withprefix,suffix,style(none/number/short/percent), anddecimalPlaces.showValuesOnSeries.Every field carries a docstring, which flows into the generated MCP tool schema so agents see exactly what's valid.
Regenerated all downstream artifacts from the source type:
schema.json,schema.py, the MCP tool Zod (services/mcp/src/tools/generated/product_analytics.ts), and the tool-schema snapshots.How did you test this code?
I'm an agent. I ran the following automated checks — no manual UI testing:
pnpm --filter=@posthog/mcp run vitest run tests/unit/tool-schema-snapshots.test.ts tests/unit/json-schema-to-zod.test.ts— pass (snapshots regenerated to include the new fields).tsc --noEmiton the MCP package — no errors in the regenerated tool file (only pre-existing, unrelated@posthog/quillmodule-resolution errors in this environment).python3 -m py_compile posthog/schema.py— pass.schema.json,schema.py, the generated Zod, and both insight tool snapshots.🤖 Agent context
Authored by PostHog Code (Claude). The task came from a session where adding a trend line to a SQL insight via MCP took longer than it should have, largely because the curated
insight-updateschema appeared to forbidtrendLine.Approach: traced the codegen chain (
schema-assistant-queries.ts→schema.json→schema.py+ generated MCP Zod) and confirmed the gap was only in the agent-facingAssistant*subset, not the backend. Rather than add onlytrendLine, I brought the agent schema in line with the backend'sChartSettingsDisplayand added per-series formatting +showValuesOnSeries, since the same friction applied to every display option. The generatedproduct_analytics.tswas updated by reproducing the deterministic codegen output (the OpenAPI step that normally regenerates it needs a full Django+DB stack) and re-running the project formatter; CI'sbuild:openapiwill reconcile it if anything drifts.Created with PostHog Code