assert_not_visible

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

Discloses critical behavioral trait: fails closed with an 'unverifiable' error instead of a false pass. Describes conditions for failure (e.g., WebView with unreadable DOM). No annotations provided, so description fully addresses behavioral transparency.

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 sentences, each essential. First states purpose, second adds critical failure mode. No redundancy or unnecessary detail.

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?

Covers key behavioral nuances (fails closed, verification conditions) for a moderately complex tool with 6 parameters and no output schema. Slight gap: does not describe the success/error return format, but error behavior is implied.

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 baseline is 3. The description adds context for some parameters (e.g., 'native a11y / WebView innerText' for text) but does not significantly augment beyond schema.

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?

Clearly states the tool asserts an element/text is absent. Provides specific behavior (FAILS CLOSED) and distinguishes from sibling tools like assert_visible and assert_text.

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 describes when the tool will fail (unverifiable absence) and passes only when a capable oracle confirms absence. Implicitly guides when to use vs alternatives.

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