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

Annotations already declare a safe, idempotent read, and the description goes well beyond them: it discloses the dual image/JSON return shape, the token cost of each image size (~1-2k for 'small'), the bbox normalization scheme and top-to-bottom sort order of elements, and the citation obligation. That is precisely the behavioral context annotations cannot express.

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?

Front-loaded with the core statement, then layered detail on return format and image sizing; every clause carries information. The long parenthetical about bbox and sorting is dense but earns its space, and nothing is repeated from the schema verbatim.

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, the description takes on the full burden of describing return values and does so thoroughly, including image sizing trade-offs. The only gap is the untied `includeElements` flag, which an agent must guess toggles the elements payload described in the text.

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 0%, so the description must carry parameter meaning; it fully explains the `image` enum ('small' ~800px/~1-2k tokens, 'full' 1800px) and implies what `elements` contains. However, `includeElements` and `screenDocId` are never explicitly addressed, so coverage of the three parameters is only partial.

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?

The opening sentence names a specific verb and resource ('One catalog screen with its image and structure'), making clear this is a single-record fetch. It contrasts implicitly with the search_* siblings via the word 'One', but never names an alternative, so an agent must infer the retrieval-vs-search split.

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?

Usage is conveyed only through downstream instructions ('look at it for color, typography and spacing', 'use them to reproduce hierarchy'), not through call-selection guidance. There is no statement of when to prefer get_screen over search_screens/search_screens_by_image or what a caller needs (a screenDocId from a search) to invoke it.

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