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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description does add real behavioral context — coverage is bounded and unknown outside published scopes, and exchange notices override tool output — but says nothing about the return shape or how partial coverage manifests.

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?

It is short, but the front-loaded sentence is opaque jargon ("civil/incoming night attribution") and "24 MO scopes" is unexplained. Four fragments that don't build a clear picture rather than one that earns every word.

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?

No output schema exists, so the description is the only source for return values, and it provides none. For a 2-parameter calendar tool whose exchange argument has no enum and whose date argument is undocumented, an agent cannot confidently construct a call from this text.

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?

With 0% schema description coverage, the description carries the full burden. It hints at valid exchange domains (Mainland China, SGX, HKEX, a cryptic "24 MO scopes") but enumerates nothing for a free-form 40-char string with no enum, and the optional `date` parameter is never mentioned at all.

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?

"Exchange-local trading date and civil/incoming night attribution" names the domain (trading calendars) but never states a verb or what the tool actually returns — a boolean trading-day check, a resolved session date, or a night-attribution object. The exchange-scope fragments ("SGX is equity/FX/rates, HKEX is cash equities") add subject matter but not a crisp purpose statement.

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 statement of when to call this versus siblings like trading_hours or next_closure. "Outside published coverage is unknown" and "Official exchange notices take precedence" are data-authority caveats, not usage guidance, and no preconditions or exclusions are given.

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