Envelope And Targets

Through MCP, siteId and pageId are top-level tool arguments, not fields in the create action. The tool strips them before dispatch and supplies pageId from the execution context. So the action body you send is:

Calling the Designer Extension API directly instead of MCP, pageId is a field on the params object rather than a separate argument. Everything else is identical.

Unknown keys on trigger.config are silently discarded

[SILENTLY-DROPPED] Any key on trigger.config that is not a declared field.

triggerConfigSchema is a plain z.object, so Zod strips unknown keys, and the object→tuple transform then re-emits only the fields it names. There is no error. The write returns success, get_interaction round-trips byte-identically, and the field you sent is gone.

Declared config fields — everything else is dropped:

Every plugin-specific field belongs inside config.pluginConfig. That is where eventName (custom), eventMode and multiTimeline (hover), and smoothness (mouse-move) live.

Why this rule leads the file: a dogfood run put three different fields at config level, watched all three vanish, and filed three capability gaps that did not exist. The docs for each field were correct and already installed. They went unread because the escalate-on-rejection habit that normally sends an agent to the reference cannot fire when the write succeeds.

So the diagnostic is: if a field you sent is absent from the response, assume you addressed it wrong before you conclude it is unsupported. timingConfigSchema is non-strict the same way — see easing-for-ease in actions-and-properties.md.

timelineDefaults is not authorable

[OMIT] on create. [REJECTED] for any non-null value, on create or update.

The Designer never dispatches a timeline-defaults update, so there is no authored value to mirror. Only null is meaningful, and only on update, where it clears a stored bag.

Guard: findTimelineDefaultsError · fragment: timelineDefaults is not authored by the Designer

An empty object does not count as “unset”. Leave the key out entirely on create.

IDs

[REJECTED] A missing action id fails schema validation before the guards run. Fragment: actions.0.id: Required

Scope

Component and variant existence is checked by the host, not by the pure guards, so a bad id fails at the responder rather than in schema validation. On update that check only runs when the call actually sends scope.

[REJECTED] A componentId no component on the site matches. Guard: findComponentScopeError · fragment: does not exist on this site

[REJECTED] A variant id that is not one of the component’s variant options. Guard: findComponentScopeError · fragment: has no variant option(s)

[REJECTED] A non-string componentId, or variants that is not an array. Guard: findScopeError · fragments: Component-scoped interactions must provide a component id / Component-scoped interaction variants must be an array

variants narrows playback, and empty means all

variants holds variant option ids, not names — the ids from the component’s variant options. Omitting the key and passing [] behave identically: the runtime reads componentScope?.variants?.length ? … : null, and the existence guard only walks a non-empty list. A non-empty list makes IX3Engine.resolveTargets apply filterByVariant on top of the component scope selector, so only instances on those variants animate.

Deleting a variant in the Designer cascades: an interaction scoped to that variant alone is deleted, and one scoped to it plus others is rewritten without it.

Do not set libraryProfileId

It is provenance, not an authoring option — isLibraryInteraction treats a scope carrying it as library-owned, and libraryDetach strips it when a library is detached. Nothing validates it, so a hand-set value silently mislabels the interaction. There is also a known bug where the field is dropped on a server round trip, which is why isLibraryInteraction falls back to asking whether the component itself came from a library.

wf:inst target parity follows scope

Under scope.type === 'component', a wf:inst target is [componentDefinitionId, elementId] and the element must exist in that definition. Under site or pages, it must be [pageId, elementId].

[REJECTED] A component-definition path on a non-component scope. Fragment: valid on component-scoped interactions

[REJECTED] A component-scoped path whose element is missing from the definition. Fragment: does not exist on this site

Scope-only updates deliberately skip this check for targets they retain, so a stored [componentDefinitionId, elementId] survives a component-to-site flip. Replacing triggers or timelines re-runs it, but only on new inst paths — you cannot invent a component-definition path on a site-scoped interaction.

Target shape

Targets are object format on the create/update wire:

A nested filterBy is always a 2-tuple, never an object:

value is [REQUIRED] even for target types that carry no value — send ''.

[REJECTED] Omitting it. Guard: findTargetValuePresenceError (via the target walk) · fragment: target.value is required

Which target keys are legal where

The full matrix is generated — see capabilities.generated.md → Targets. The rules behind it:

[REJECTED] wf:id in any context. Guard: findDisallowedTargetKeyError · fragment: is not offered by the Designer (shouldShow: false in all contexts)

[REJECTED] Action-only keys (wf:trigger-only, wf:trigger-only-parent, wf:any-element) used as a trigger target, or as a Filter-by on a trigger-side target. They bind against no trigger element and never fire. Fragment: is only valid on timeline actions

[REJECTED] wf:trigger-only-parent as a base target type. It is Filter-by only.

[REJECTED] A key the Filter-by picker does not offer, used inside filterBy. Guard: findDisallowedTargetKeyError with asFilterBy · fragment: is not offered by the Designer's Filter-by picker

[REJECTED] An active filterContext on wf:trigger-only or wf:inst — the Designer hides the Filter UI for those base types. Fragment: does not support Filter; the Designer hides Filter UI for this target type

A stamped filterContext with relationship: 'none' is accepted on those keys. Only a filter with a real relationship is refused. This distinction matters on read-then-write flows, where the stored value already carries the stamp.

[REJECTED] wf:any-element with filterContext.relationship === 'none'. Guard: findAnyElementFilterError

[REJECTED] firstMatchOnly: true together with relationship: 'none'.

[REJECTED] A DirectScope or SelectorScope wrapper on a Designer-authored wf: target, whether or not a filter is active. The Scope dropdown is unreachable in the native Designer, because create always stamps a none-filter 3-tuple and the panel hides Scope for any stamped target. Narrow to a matching set with Filter instead. Guard: validateTargetValue · fragment: does not support Scope

A malformed scope wrapper reports separately as target scope must be a valid DirectScope or SelectorScope.

filterContext.relationship — the full enum

Eight values. A wrong one is rejected with an enum-listing Zod message, so this is the cheap kind of mistake — but a CSS-flavoured guess like descendants reads as obviously correct, so check the list rather than inferring.

These are the panel’s authoring names. The published runtime uses a different internal vocabulary — all, parent, children, siblings, next, previous, first-ancestor, first-descendant, descendants, ancestors — and the host maps between them. Reading the runtime bundle and copying those names back into a write is a trap: descendants looks like a real value because it is one, just not on this side of the boundary.

The stamped filterContext

When a caller omits filterContext on an element-scoped target, the host stamps the Designer’s placeholder:

Prefer omitting it and letting the host stamp, rather than composing it yourself.

Class targets

Style-block UUIDs are preferred over class-name slugs — they round-trip through the panel reliably. Class name strings are accepted.

Through MCP, resolve one with data_style_tool: get_styles or query_styles returns each style’s id, and that UUID is what goes in the value array. Note data_style_tool requires both siteId and pageId, so do the page lookup first.

Calling the Designer Extension API directly instead, the equivalents are webflow.createStyle and getStyleByName.

One wf:class target is one compound selector, so the ids are ANDed

The id array is not a list of alternatives. Publishing joins every id’s class name with a dot (transformClassTargetValue → .join('.')) and the runtime resolver queries .${value}, so ['a', 'b'] becomes the selector .a.b and matches only elements carrying both classes.

That is exactly why a combo class works. The host expands each id’s ancestor chain on write (resolveComboClassParents, via withComboParents in ix3ClassTargets.ts), so passing the single id for .card.featured stores both ids and resolves to .card.featured — the selector that combo already styles. Pass the one leaf id and let the host expand it. Do not assemble the chain yourself.

[REQUIRED] in practice: the resulting ids must form a single combo chain. Two ids from different chains produce a selector no element carries, and the target resolves to zero elements. Nothing rejects it — isValidStylePath guards element.setStyles, not IX3 targets — so the interaction saves, reads back with both ids intact, and never runs.

The shape to watch for is one leaf class name reused across different parents, for example a lift combo that exists as both .btn.lift and .btn.cta.lift. Those are two distinct style blocks with the same name. Passing both ids expands to the union of their parents and asks for an element carrying btn, cta, and lift at once, which is only the second element — or, if the parents diverge, nothing.

So: one target means one class or one combo chain. Two different sets of elements means two targets or two actions. When several elements need to animate differently, give each its own class rather than reusing one name across chains.

[REJECTED] A class-name string whose name matches more than one style block — which is precisely the reused-leaf-name case above. The host cannot pick for you. Resolver: resolveWfClassBase · fragment: matches multiple style blocks; use a style-block id array instead

[REJECTED] A name that matches no style block on the site (does not match a style block on this site), and an id array containing an id that is not a class style block on the site (is not on this site).

Value shapes per target type

validateTargetValue enforces a per-key value shape shared with the DE responders. It rejects, for example, a string where an id array is expected. Fragment varies by key; the message names the expected shape.

wf:any-element is the one target key whose value is a wildcard rather than a placeholder. The three action-only keys look interchangeable and are not: sending '' on wf:any-element is refused with "wf:any-element" value must be "*", while wf:trigger-only and wf:trigger-only-parent do take ''. Because these keys are usually authored as a batch — one row per filterContext relationship — getting this wrong loses the whole batch at once rather than one row.

wf:attribute takes a bare name or a full selector. A bare name ('data-thing') is accepted and stored as [data-thing], which matches every element carrying that attribute. Pass a full selector ('[data-thing="x"]', stored verbatim) when several elements share the attribute and you mean one of them.

Two more are the ones agents get wrong.

wf:inst is a 2-tuple, not a bare element id. For an element that lives on a page rather than inside a component definition, the componentId slot is the page id:

[REJECTED] A bare string. Fragment: wf:inst value must be [componentId, elementId]

Which of the two forms is legal is not a free choice — it follows scope. See wf:inst target parity follows scope.

wf:selector is how you reach the body from an action. wf:body is trigger-context-only, so an action target has to use a selector instead:

[REJECTED] wf:body as an action target. Guard: findActionTargetContextError · fragment: is a trigger-context-only target and cannot be used as an action target

The message names the fix, which is the only reason wf:selector is discoverable at all — it appears in no capability table.

autoReverse is not authorable either

[REJECTED] action.timing.autoReverse and timeline.settings.autoReverse. Neither the action timing editor nor the timeline settings UI writes them, and the runtime reverses with playInReverse instead.

Guard: findTimingAutoReverseError · fragment: is not authored by the Designer; the runtime uses playInReverse

Do not read that message as an instruction. It names playInReverse because that is what the runtime reads, not because it is something to author. playInReverse is a timeline-level boolean the Designer does not write, and #118489 (opens in a new tab) rejects it on create and on a timeline-replacing update with playInReverse is not authored by the Designer, grandfathering an unchanged stored value the same way autoReverse is.

So there is no API-side replacement for autoReverse. Author the reverse as its own tween, or use a trigger control that plays backwards. Do not reach for a timeline flag.

This is the trap the message sets: “the runtime uses X” reads as “use X”, and X sits at a level the sentence never names, so an agent guesses across the trigger, the action, and the timeline before finding that none of them accept it.

[LEGACY-OK-ON-UPDATE] An unchanged stored value on the same id passes. The panel has no control that clears one either, and get() returns it, so rejecting it outright would strand any interaction that already carries one on its next read-modify-write. A new or altered value still rejects.

Mouse-move persist bounds

[REJECTED] wf:mouse-move pluginConfig.smoothness outside its millisecond range, or restingState x/y outside 0 to 100. Absent keys are legal. Guard: findMouseMoveRangeError

Note the two numbers differ: the Smoothness slider in the panel is 0 to 100, while the persisted bound follows the number input. The generated bounds table has the current values.

Size

Every target value, filter value, and condition value shares one interaction-wide byte and node budget. See limits-and-budgets.md.

• references/envelope-and-targets.md(opens in a new tab)
• Raw file(opens in a new tab)
• webflow/webflow-skills(opens in a new tab)