Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare destructiveHint=true and openWorldHint=true, and the description adds meaningful context on top: it specifies the destructive behavior is a replacement of that language's screenshots for this device size, that it never submits for review, and that an external auth connection to App Store Connect is required. That is exactly the extra behavioral detail annotations cannot convey.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Three tight sentences front-loading the action and scope, then exclusions, then prerequisites and the fallback. No filler or repetition of the title.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema and a small parameter set, the description covers the key agent-facing concerns: what is overwritten, that review submission is out of scope, auth prerequisites, and the create_version fallback path. Minor gaps remain around error/partial-failure behavior and the locale parameter's role, but nothing critical is missing for correct invocation.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is only 33% (only set_id is documented), so the description must compensate. It usefully explains create_version's purpose and the condition for setting it, but never names or explains the locale parameter beyond the oblique phrase 'that language's screenshots'. Partial compensation warrants the 3 baseline-and-hold.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (upload) plus resource (unlocked set) and destination (the app's editable version in App Store Connect), and narrows scope to one language's screenshots for one device size. This clearly separates it from siblings like export_set, upload_screenshots, and design_set.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives a concrete precondition (user must have connected App Store Connect in Agent C) and an explicit branch for the missing-editable-version case, including telling the agent to ask the user first. It does not contrast against sibling tools such as export_set or upload_screenshots, so it stops short of full when/when-not/alternatives coverage.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.