session_stats

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

Annotations already declare readOnlyHint=true, so the safety profile is covered by structured data. The description adds nothing beyond that: no scope of the 'session' (does it reset, per-conversation?), no note that it takes no arguments, and no hint of what is counted.

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?

A single short sentence with no padding, and the subject is front-loaded. The model-directed phrasing ('Tell the user') is slightly unusual for a tool description but does not waste space.

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 carries full responsibility for describing the return value, and it provides none — the agent cannot know what statistics come back or in what form. For a session-reporting tool the description is too thin to be complete.

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 tool takes zero parameters, so the baseline of 4 applies. There is nothing for the description to clarify about arguments.

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 verb and resource ('tell the user about the tool usage during this session'), so the general intent — report on tools used in the current session — is inferable. However, it never specifies what 'tool usage' means (calls per tool, timing, errors) and does nothing to distinguish itself from the surrounding scraper/browser siblings.

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?

There is no indication of when to invoke this versus any alternative, no trigger conditions, and no note that it is a meta/reporting tool rather than a scraping one. The agent must guess the use case entirely.

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