Office.js provides no way to detect unsupported APIs within supported requirement sets

Problem Statement

Currently, the only documented mechanism to check for annotations support is Office.context.requirements.isSetSupported('WordApi', '1.8').

However, on perpetual / non-subscription Office builds (e.g., Office 2021, Office 2024, LTSC), isSetSupported('WordApi', '1.8') evaluates to true, yet calling document.getAnnotations() immediately throws a runtime error (NotImplemented / GeneralException).

There is currently zero way for an add-in to detect whether the user is on a perpetual build or whether getAnnotations() will fail before actually calling it.

Why This Is Unacceptable

1. Broken API Contract: isSetSupported() is advertised as the canonical capability-detection mechanism. Gating individual functions behind license tiers while marking the entire requirement set as "supported" defeats the purpose of requirement sets and leads to false positives.
2. Impossible to Build Resilient UI: Add-ins cannot hide, disable, or adapt UI elements conditionally on startup because there is no API to check if getAnnotations (or the underlying license tier) is supported.
3. No Viable Pre-Check: Developers cannot safely query capabilities upfront. Relying on blind runtime failures (try/catch on first invocation) produces broken user experiences, unneeded error telemetry, and brittle add-in logic.

Required Solution

Office.js must provide a reliable, deterministic way to detect whether an individual API or feature is usable before invoking it.

We need Microsoft to implement at least one of the following:

1. Method / Feature-Level Detection: Provide a granular capability check, for example:
   • Office.context.requirements.isMethodSupported('Word.Document.getAnnotations') -> boolean
   • or Word.isFeatureSupported('Annotations') -> boolean
2. License / SKU Awareness: Expose host license properties on the context object so add-ins can identify perpetual/non-subscription environments upfront, for example:
   • Office.context.license.isSubscription -> boolean
   • or Office.context.license.skuType -> 'perpetual' | 'subscription'

Reference

GitHub Issue: https://github.com/OfficeDev/office-js/issues/5701