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

Annotations only declare it read-only and non-destructive; the description adds that the result is live data and enumerates the returned fields (offset, abbreviation, DST status). It does not say how unknown or ambiguous place strings are handled, which is the main behavioral risk for a lookup tool.

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 short sentences, front-loaded with the trigger and ending with the argument formats. The final sentence partly restates the schema's examples, which is the only redundancy, and nothing is bloated.

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?

One required parameter, no output schema — and the description compensates by naming the return fields explicitly. Combined with the never-guess warning, an agent has everything needed to call this correctly without additional context.

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 a format the schema does not mention — "UTC+5:30" fixed-offset strings — alongside cities, IANA zones and abbreviations. That extra accepted-input form has real selection value for an agent picking the right argument syntax.

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?

"Returns the real current time, date, UTC offset, abbreviation and daylight saving status for each place" states a specific resource (current time/date per place) and the exact output. The word "now" plus the multi-place framing clearly separates it from siblings like meridian_convert_time and meridian_zone_info.

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?

"Use when you need to know what time or date it is right now somewhere" plus "You have no clock of your own, so never guess" gives a clear trigger and a warning against the main failure mode. It does not explicitly name convert_time or zone_info as the alternatives when the question is not about the present moment, so routing guidance is implied rather than stated.

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