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

With no annotations, the description carries the full burden and does disclose meaningful behavior: the default call returns a trend rather than the full table, caveats are always attached, and some epochs are withheld from the series for undersampling. It does not cover permissions, rate limits, or the exact shape of the returned payload.

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?

Three dense sentences, front-loaded with what the series is before describing call modes. Every clause carries information — scope, default behavior, mode switches, and the caveat obligation — with no filler.

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?

There is no output schema and no annotations, so the description has to stand alone; it does describe what comes back (trend + caveats, not the full table) and how to select slices. The remaining gap is that the concrete response structure for each mode is not described.

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 100%, so the baseline is 3, but the description adds real meaning: it explains that `epoch` yields a single data point, `series: true` yields the full set, and `withheld: true` exposes the epochs excluded for n < min_n. That interplay (a filtered series vs. the withheld remainder) is the key semantic the schema alone does not convey.

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 names a concrete resource and metric: the share of sites whose robots.txt takes a stance on AI agents, indexed by Common Crawl epoch. It is specific enough that an agent can tell it apart from host_report or bulk_export by scope ('single vantage'), though it never explicitly names or contrasts a sibling.

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?

Explicit invocation modes are given: no args returns the trend plus caveats (not the whole table), `epoch` returns one point, `series: true` returns all epochs, `withheld: true` returns the undersampled epochs. It also gives a usage instruction ('read them before quoting a number'). What's missing is guidance on when this metric is preferable to a sibling tool's output.

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