get_screen_size

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

No annotations provided, so description carries the burden. It discloses return format, coordinate system (absolute pixels, top-left origin), and failure case. Does not explicitly state it's a read-only operation, but that is implied.

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 concise sentences front-loading the key information: what it returns, when to call it, and how to interpret vision. No wasted words.

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?

The description covers return schema, usage context, coordinate system interpretation, and failure condition. For a tool with one optional parameter and output schema, this is fully complete.

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 description must compensate. The parameter 'instance' is referenced in 'within THIS instance's display' but not explicitly listed or described. Does not explain default or behavior when omitted.

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 description clearly states it returns screen size, vision backend, and server version. It also distinguishes itself from siblings like screenshot and parse_screen by explaining how vision tells you which to use.

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?

Explicitly says 'Call it once before coordinate math' and provides conditional guidance on how to use based on the vision field. Also mentions failure condition (isError) when instance is down.

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