perch_snapshot

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

No annotations are provided, so the description carries the burden. It discloses useful behavior: output is a text list of visible interactive elements with CSS selectors, scoped to the live preview, implying a non-mutating read. It does not state prerequisites (a started/running preview), whether results reflect off-screen or hidden elements, or any size/performance limits, leaving real gaps for an annotation-free tool.

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 tight sentences, front-loaded with the core action and followed by the differentiating usage rule. Every clause earns its place; nothing is restated from the name or schema.

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?

There is no output schema, so the description usefully compensates by describing the return shape (visible interactive elements, each with a CSS selector). With three optional, fully schema-documented parameters and no annotations, the only meaningful omission is the prerequisite that a live preview must exist and how frames interact with it.

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%, with frame (enum), limit, and filter all documented in the schema, so the baseline is 3. The description adds no parameter-level detail beyond the schema — it never mentions frame selection, the 250 default limit, or label/tag filtering — so it neither helps nor hurts.

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 (visible interactive elements: buttons/inputs/links) scoped to the live preview, and adds the returned artifact (a ready-to-use CSS selector per element). It also distinguishes itself from the screenshot sibling ('instead of screenshots'), so an agent can route between perch_snapshot and perch_shot without opening either schema.

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?

'Use this instead of screenshots to find what to click' gives explicit when-to-use guidance and names the alternative approach implicitly (screenshots = perch_shot), and pairs naturally with perch_click/perch_type downstream. It stops short of stating exclusions or prerequisites (e.g. preview must be running via perch_start), so it is clear context rather than full when/when-not coverage.

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