describe_ui

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

Annotations declare readOnlyHint=true, so no contradiction. The description adds value by disclosing the default filtering behavior (only elements with text/desc or interactive) and the output fields (bounds, tap centers), which is useful context beyond the annotation. It doesn't mention potential performance or device requirements, but the read-only nature is covered.

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 with zero redundancy. The main purpose is front-loaded, followed by a concise note on default behavior. Every word adds information; no filler.

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 simple read-only tool with three optional parameters all documented, the description is complete enough. It specifies the output type and default filtering, which covers the agent's needs for invoking the tool correctly. The lack of an output schema is acceptable given the compact and well-described return format.

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 coverage is 100%, so all parameters are already well-documented. The description adds marginal value by reiterating the default filtering that relates to include_all, but it doesn't provide deeper meaning beyond the schema. The baseline of 3 is appropriate since the schema carries the semantic load.

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 ('Get'), a clear resource ('UI hierarchy of the current screen'), and the output format ('compact JSON list') with detailed content fields. This clearly distinguishes it from siblings like screenshot (which captures an image) and find_element (which searches for a specific element).

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 its purpose (inspect UI hierarchy) but does not explicitly mention when to use it instead of alternatives like find_element or screenshot. It does clarify default filtering behavior, which hints at usage for interesting elements vs all nodes, but lacks explicit exclusions or comparisons.

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