get_screen

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

With no annotations, the description carries the full burden. It discloses that the tool returns a text-mode snapshot with elements formatted as `[id] class "label" kind@(x,y)` plus the screen hash, and that ids are stable for later use. This gives meaningful insight into the tool's output behavior, though it stops short of detailing prerequisites or edge cases like device connection errors.

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?

The description is two sentences, about 40 words. It front-loads the core purpose and then details the return format and the relevance of stable ids. Every sentence adds value without redundancy or fluff.

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 tool has only 2 optional parameters with full schema descriptions and an output schema (per context signals). The description supplements this by explaining the output line format and the screen hash, which is useful beyond the schema. It is complete enough for an agent to correctly invoke the tool, though it could optionally mention default mode behavior or device‑related failures.

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 100% for both parameters (mode and device), each with clear descriptions. The tool description adds no additional parameter semantics beyond the schema, so the baseline of 3 applies. The mention of 'compact' in the description aligns with mode defaults but does not extend the schema's meaning.

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 a specific action: 'Capture a compact text-mode snapshot of the current screen.' This distinguishes it from siblings like get_screen_hash (which only returns a hash) and tap (for interactions). The return format is explicitly described, reinforcing the tool's unique role.

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 description provides clear context: it returns stable element ids that can be used with tap(). This implies when to use the tool (when you need to inspect or interact with screen elements). It does not explicitly mention alternatives or exclusions, but the sibling context and the stable-id feature effectively steer usage.

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