n8n/packages/@n8n/instance-ai/knowledge-base/reference/trigger-input-data-shapes.md

Per-trigger inputData shape

Used by verify-built-workflow, executions(action="run"), and checkpoint verification. The pin-data adapter spreads or wraps based on trigger type — passing the wrong shape gives null downstream values that look like an expression bug.

Form Trigger (n8n-nodes-base.formTrigger)

Flat field map, e.g. {name: "Alice", email: "a@b.c"}. The production Form Trigger emits each field directly on $json, so the builder's $json.<field> expressions are correct. Do NOT wrap in formFields — the adapter will reject the call.

Webhook (n8n-nodes-base.webhook)

The body payload, e.g. {event: "signup", userId: "..."}. The adapter wraps it under body, so downstream nodes reference $json.body.<field>.

Chat Trigger (@n8n/n8n-nodes-langchain.chatTrigger)

{chatInput: "user message"}.

Schedule Trigger (n8n-nodes-base.scheduleTrigger)

Omit inputData; the adapter emits synthetic timestamp fields.

Other event triggers

Linear, GitHub, Slack, MCP, and similar triggers: pass inputData matching the trigger's expected payload shape from the node type definition.

Debugging wrong null values

Do not patch a workflow first when verify returns null downstream values. Re-run verify with the corrected inputData shape. Only patch the workflow if the expression is wrong against the production trigger output shape (consult node descriptions), not the instanceAi pin data path.