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

With no annotations, the description must carry the full behavioral burden. It conveys read-only semantics and what is returned, which is useful, but says nothing about behavior when no accounts are signed in, whether the slot index is stable, or that the output is session-local and may be empty.

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 short sentences, zero filler. The purpose is front-loaded and the constraint ('only') closes it out efficiently.

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 parameterless read-only listing with no output schema, the description tells the agent what the call returns and why to use it. Minor gap: no hint about empty results or that the data is purely diagnostic, but nothing critical is missing for correct invocation.

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 description coverage is 100% and there is only one optional parameter (notification_message), so the schema already does the explaining. The description adds nothing about it, which is acceptable at baseline 3 but no better.

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 ('List which Google accounts are signed in') plus the exact data returned ('X-Goog-AuthUser slot index'). The scope is tightly bounded to 'this browser session,' which implicitly separates it from siblings like start_browser_auth and refresh_browser_session, though no sibling is named 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?

'For visibility/debugging only' gives a clear usage context and a soft exclusion (don't build on this for auth logic). It stops short of naming an alternative tool (e.g., refresh_browser_session) for when the agent actually needs to fix a stale session.

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