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

Annotations already declare readOnly, idempotent, openWorld, non-destructive, so safety is covered. The description adds the one behavior annotations cannot convey: this call is free while the downstream snapshot costs money. It does not say what a failed validation returns or whether validation guarantees success.

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 sentence, front-loaded with the most decision-relevant fact ('Free:'), with zero 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?

For a 4-parameter, no-required-param tool with an output schema, the description covers the core purpose and cost trade-off, but leaves half the parameters unexplained and says nothing about what a failed validation looks like.

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 only 25% (only 'date' is annotated), so the description does some compensating work by flagging 'date in range' and 'enough history' (likely min_age_days). The other two parameters, top_n and min_avg_dollar_volume, get no explanation in either place.

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 ('check') and resource ('universe_snapshot arguments') plus the two checks performed: date in range and enough history. It clearly distinguishes itself from the other validate_* siblings by naming universe_snapshot, though it never says so 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?

'before paying' gives an explicit precondition for calling this tool, i.e. always run it before universe_snapshot. It is not spelled out as a when-not rule or naming alternatives, keeping it below a 5.

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