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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds useful behavioral context by specifying the return format: 'compact text with [N] indexes.' It does not describe edge cases or limitations, but for a simple read-only tool with annotation support, this is adequate.

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 two concise sentences with no filler. The core behavior ('Get the current page state') is front-loaded, and the return-format detail is provided efficiently. Every sentence earns its place.

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-parameter read-only tool with no output schema, the description provides enough information to call it correctly: what it returns, the format ([N] indexes), and its intended downstream use. It does not describe the exact structure of an element entry, but this is a minor gap given the simplicity of the operation.

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?

The only parameter, session_id, is already documented in the schema with a description, giving 100% schema description coverage. The tool description does not add additional meaning about the parameter. Baseline 3 applies because the schema carries the parameter documentation burden.

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 states a specific verb and resource: 'Get the current page state as an indexed list of interactive elements.' It clearly differentiates this from the action-oriented sibling tools (session_click, session_input) by positioning itself as a read-only state retrieval tool. The mention of 'for use with click/input tools' strengthens its identity as the preparatory inspection tool.

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 conveys when to use the tool: before invoking click/input tools, to obtain the [N] indexes needed for those actions. It does not explicitly name alternative tools or state exclusions, but the context is clear and sufficient for an agent to select it over mutation-focused siblings.

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