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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive, so the safety profile is covered. The description adds useful context beyond that — that it reads only VISIBLE text and that it is the assertion primitive for on-screen content. It stops short of describing error behavior or how large/whole-page output is bounded, keeping it below a 5.

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 tightly packed sentences: scope first, then purpose, then the sibling exclusion. Every clause earns its place with no filler or redundancy.

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 read-only text-extraction tool with full schema coverage, rich annotations, and no output schema, the description supplies the remaining essentials: target surface, scope, assertion purpose, and device-vs-desktop routing. An agent has everything needed to call it correctly.

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 both pageId ("Page ID from web_navigate") and selector ("CSS selector; omit for the whole page body") are already documented. The description reinforces the selector-omission behavior but adds no new syntax or format detail, so the baseline 3 applies.

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+resource (read visible text), the exact target surface (the DESKTOP grid browser, by pageId), and the scope (one element or the whole page). It also explicitly separates itself from webpage_get_text, so an agent can route between the two 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?

Gives explicit when-to-use ("This is how you ASSERT on what is actually on screen"), the selector-omitted case for whole-page reads, and a clear when-not/alternative ("Not a device — for a phone or tablet use webpage_get_text (by udid)"). Nothing is left to inference.

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