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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety is covered. The description adds genuinely useful scope context ('anywhere', i.e. no filtering, and that a timestamp accompanies the result), but says nothing about behavior when nothing has been spotted, staleness of the 'most recent' value, or response shape.

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 tight sentences with zero filler: what it returns first, intended use second. Nothing could be cut without losing information.

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 parameters, no output schema, and full annotation coverage, the description supplies the one thing structured fields cannot: that the result is global (anywhere) and carries a timestamp. Minor omission is what happens on an empty/never-observed state.

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 no parameters, so there is nothing for the description to disambiguate; baseline 4 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 resource and scope: the single most recent table seen open anywhere, plus the timestamp it was spotted. It is distinguishable from siblings like hardest_tables or when_does_it_release, though it never names or contrasts with the overlapping-sounding open_now.

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?

It gives two intended uses ('show the service is live', 'a sense of what is moving right now'), which implies a liveness/pulse-check role. However it offers no when-not guidance and does not address how it differs from the sibling open_now, which an agent could easily confuse it with.

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