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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, covering the safety profile. The description usefully adds that the output is text enumerating roles, labels and states, but says nothing about behavior on large pages, truncation, or whether it requires the page to be fully loaded.

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?

Three short paragraphs, front-loaded with the core action. There is mild redundancy between the second and third paragraphs, which both describe what the tree contains, but no wasted 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?

With no output schema, the description correctly shoulders the job of describing return contents (roles, labels, states, selectors). It is nearly complete for a read-only single-param tool, missing only edge-case behavior like tree size limits or loading prerequisites.

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?

There is a single required parameter (session_id) whose schema description is 100% covered ('Session ID returned by browser_navigate'). The description adds no further parameter meaning, 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 and resource ('Get the ARIA accessibility tree of the current page') and characterizes the output as readable text. It implicitly differentiates from the screenshot sibling by noting the token advantage, but it never names an alternative tool explicitly.

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?

Provides usable context: use it to see page structure and the selectors needed to drive interactions, and it is cheaper in tokens than a screenshot. It stops short of explicit when-not conditions or naming competing siblings like browser_get_html or browser_get_text.

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