download_ui

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

With no annotations, the description carries the full burden; it does disclose meaningful behavior — the write destination (UI_LIBRARY_DIR, default ~/.ui-library) and that already-downloaded and paywalled screens are skipped. It omits whether existing content is overwritten, whether authentication/network access is required, and what happens on partial failure, leaving a significant gap for a mutating tool.

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?

A single dense sentence with the destination and default front-loaded in a parenthetical, followed by the two selection modes and the skip behavior. No filler; every clause earns its place.

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?

For a 4-parameter, no-output-schema tool, the description covers destination, selection modes, and skip semantics adequately. Minor gaps remain around return values (count, paths) and how source selection interacts with appId/query, but nothing critical to correct invocation is missing.

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 50% (limit and source have descriptions; appId and query do not). The description adds real meaning by distinguishing appId ('every screen of an appId') from query ('the results of a query'), but says nothing about the source enum or the limit default, so it only partially compensates.

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 (download) and resource (screens into the local UI library) and spells out the two selection modes: all screens of an appId, or query results. It is clearly distinct from read-only siblings like search_ui/get_ui_screens, but it never names those alternatives explicitly, keeping it short of a 5.

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?

The 'appId vs query' phrasing implies which mode to use for which need, and the skip rules imply idempotent re-runs are safe. However, there is no explicit guidance about when to call this versus search_ui, library_search, or get_ui_screens, so the agent must infer the routing.

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