Screenshot

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

With no annotations, the description carries full behavioral disclosure burden. It explicitly notes 'Rendered in-process by the app — no Screen Recording permission', which is valuable permission/auth context. It also clarifies the scope (whole window or single node). It doesn't mention side effects, but the action is read-only and the description implies no data mutation.

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?

Two compact sentences with zero filler. The primary action and output are stated first, followed by the important permission detail. Every word adds value.

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 tool with two optional parameters and a straightforward output (PNG), the description provides sufficient information for correct invocation. It doesn't specify the exact return format (e.g., file path vs binary data), but 'to PNG' strongly implies the output is an image. Given no output schema, a brief note on return format would improve completeness slightly, but it's not a critical gap.

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 description coverage is 100%, so the parameters are fully documented in the schema. The description adds minimal extra meaning beyond restating the selector concept ('via `selector`') which is already in the schema. The baseline of 3 applies since the schema fully covers parameter semantics.

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 uses a specific verb ('Render') with a clear resource ('a window or a single node') and output format ('PNG'). It clearly differentiates from siblings like get_ui_tree (which retrieves structure) and click/type (which perform actions) — this is the only tool that captures visual output.

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 purpose is self-evident: when an agent needs a visual representation of a window or node, this tool is the obvious choice. No alternative is mentioned, but given the sibling list, no other tool does this. It doesn't provide explicit when-not-to-use guidance, but the context is clear enough.

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