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

Adds substantial context beyond the annotations: the hover is synthetic and not persisted, hidden captions are omitted before hovering, events are not isTrusted, and the revealed text is ephemeral. This is genuinely useful for an agent interpreting results. The readOnlyHint=false framing is somewhat ambiguous for a non-mutating inspection action, but the description doesn't contradict it.

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?

Front-loads the action, then the requirements, then the key caveats about ephemeral revealed text. Mostly dense and purposeful, with only the parenthetical example adding mild slack.

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 usefully explains the return value (textSummary including newly visible caption/tooltip text) and the ephemerality caveat. It is nearly complete, lacking only fuller explanation of the observation/element identifier semantics and error behavior.

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 only 25% (only idempotencyKey is documented), so the description should compensate more. It lists the three required parameter names and implies observationId ties to "the latest observation," but adds no format or meaning for sessionId/elementId beyond what the schema already shows via pattern and length constraints.

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 ("Hover a semantic element from the latest observation") and clarifies the underlying events (mouseover/mouseenter). It is clearly distinguishable from siblings like browser_click or browser_select by the action itself, though it never explicitly contrasts itself with them.

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?

Gives a clear operational context (use it to reveal caption/tooltip text) and an important consumption rule: the revealed text is only on this result and is gone from the next browser_observe, so the agent must read it now. It doesn't state explicit when-not-to-use or name an alternative tool, which keeps it below a 5.

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