why_did_element_disappear

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

No annotations are provided, so the description carries the burden of behavioral disclosure. It usefully lists the diagnostic dimensions it can report: removal mechanism, ancestor container destruction, style changes, and correlated errors/network triggers. However, it does not state whether the operation is read-only, what kinds of limitations exist, or what the output format will be.

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?

The description is a single dense sentence with no filler. The purpose is front-loaded ('Forensic root-cause diagnosis') and each phrase contributes meaning: injected/existing, disappeared, removal mechanism, ancestor container destruction, style changes, and correlated errors/network triggers.

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?

The description provides enough orientation for an agent to decide when to invoke the tool and what it will return conceptually. It covers the tool's focus areas, and the 100% parameter schema coverage handles invocation details. The only gap is the absence of an explicitly described output shape, but the listed diagnosis dimensions largely compensate for the missing output 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 100% for the two parameters, so the schema already fully documents sessionId and target. The description adds no parameter-specific guidance beyond the contextual phrase 'target element', which is already covered by the schema's own description.

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?

The description uses a specific verb phrase ('Forensic root-cause diagnosis') and clearly identifies the resource and outcome: determining why an injected or existing UI element disappeared. It also differentiates the tool from session-management siblings by focusing on disappearance cause analysis.

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 description implies when to use the tool (whenever a UI element disappeared and the cause is unknown), but it does not explicitly state when not to use it or name alternatives such as get_element_visual_state or get_live_dom_snapshot. The usage context is inferrable but not made explicit.

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