Assert visible

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

Annotations declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds genuinely new behavioral context beyond the annotations: the PASS/FAIL outcome model, the timeout window, and critically that failure surfaces as isError. That failure-signaling detail is valuable and not in the annotations.

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?

A single, front-loaded sentence that delivers the core semantics (pass condition, the visible=false inversion, timeout, fail signaling) with zero filler. The parenthetical is well-used to pack the edge case efficiently.

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 single-assertion tool with full annotations and a 100%-covered schema, the description conveys everything needed to invoke it correctly, including the failure mode. No output schema exists but the description states the return semantics (PASS / isError). Minor absence of explicit 'when to use vs wait_for' keeps it just under top marks.

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 parameters (frame, label, timeout, visible, selector) are already documented in the schema itself. The description restates the visible=false inversion behavior and timeout, which mirrors the schema rather than adding new syntax or edge-case meaning. Baseline 3 is appropriate.

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 and resource: it asserts element visibility, with pass/fail outcomes spelled out. It's clearly distinguishable from the sibling assert_text (which checks text content) and wait_for (which just waits). An agent can tell exactly what this does without opening the 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?

The 'Test assertion' framing implies this belongs in a test/verification context, contrasted implicitly against the action tools (click, fill) in the sibling list. However, it never explicitly says when to prefer this over wait_for or assert_text, nor any exclusions. Usage is implied rather than stated.

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