list_screens

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

With no annotations and no output schema, the description does useful work by naming the returned fields (ids, labels, sizes, focused flag), which signals this is a non-mutating enumeration. However, it doesn't state whether display state can change mid-call, what 'focused' means if no display is focused, or any permission requirements.

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 sentence with the resource and the payload described up front and zero filler. Every clause ('every connected display', the field list) carries information an agent needs.

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 zero-parameter, no-output-schema tool, the description covers the return shape and scope well enough to call it correctly. The only remaining gap is the unaddressed relationship to get_focused_screen.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies. The description correctly frames this as a whole-system enumeration rather than a filtered query.

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 ('List') and resource ('every connected macOS display') and enumerates what each entry contains (ids, labels, sizes, focused flag). It is clear without opening the schema, though it doesn't explicitly distinguish itself from the sibling get_focused_screen, which returns a subset of the same information.

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 only implied: an agent can infer this is the tool for enumerating all displays. There is no explicit statement of when to prefer it over get_focused_screen (which returns just the focused display) and no prerequisites or exclusions noted.

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