scroll

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

With no annotations, the description carries the full burden and does so: it documents the 20000-pixel-per-call clamp and sign convention, the lazy-list growth behavior, the settled-position reply fields (scroll_y, scroll_height, at_bottom), and the fast-fail codes for selector (not_found, hidden, disabled, timeout, page_closed).

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?

Front-loads the mutually-exclusive-argument rule, then uses terse bullets for each mode and a short paragraph for edge cases. Every sentence carries operational information; nothing restates the tool 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?

For a scroll tool with an output schema, the description covers the core invocation contract, the lazy-load repetition case, the no-movement fallback, and selector failure modes. The remaining gap is the three unexplained auxiliary parameters (reason, confirm, timeout_ms), which leaves the tool slightly incomplete for an unannotated 6-parameter schema.

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 0% across 6 parameters, so the description must compensate, and it only covers three: to, by_y (with sign/limit semantics) and selector. reason, confirm, and timeout_ms are left entirely undocumented in both schema and description, so an agent cannot infer their expected values.

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?

Opens with a specific verb+resource ('Scroll the page') and immediately narrows the invocation contract ('Give exactly one of to, by_y or selector'). This is clearly distinct from siblings like click, navigate, and read_page, and the three modes are individually defined.

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 routes usage: to='top'/'bottom' for document ends, by_y for pixel wheel movement, selector to bring an element into view. It also prescribes re-calling scroll(to='bottom') on lazy-loading pages until the reply says at_bottom, and tells the agent what to do when a scroll moved nothing (try selector for inner panels).

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