List output sizes

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

Annotations already declare readOnly/idempotent/non-destructive and closed-world, so the description adds real value on top: zero credit cost and the default hidden-deprecated filtering with 'replacedBy' metadata. What's missing is any note on result size or ordering, but for a small enumeration list that's minor.

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 purpose, then a labeled 'When to use' clause, a credits note, and a default-behavior note — each line carries distinct information with no filler.

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?

An output schema exists, so return values need not be re-explained, and the description still names the key fields. For a free, read-only, three-optional-parameter enumeration tool, nothing an agent needs to call it correctly is absent.

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?

With only 33% schema coverage the description must compensate, and it does: it explains includeDeprecated's effect and the replacedBy field, and it defines the allowed 'kind' values (screenshot or feature_graphic), with 'store' documented in-schema. All three parameters are covered.

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+resource ('Lists the output sizes (device ids)') and enumerates the returned fields (id, store, kind, pixel size, orientations), so the agent knows exactly what comes back. It also scopes the domain to the two supported stores, distinguishing it from get_store_requirements.

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?

An explicit 'When to use' clause names the downstream tools whose parameters this feeds ('device' for generate_screenshot, 'devices' for create_screenshot_set), and it routes the agent to get_store_requirements for the distinct question of which sizes a store requires. Both the use case and the alternative are stated.

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