Today

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

Annotations already declare readOnly, idempotent, non-destructive and open-world behavior, so the safety profile is covered. The description adds useful context the annotations don't: the fixed Tehran timezone, the multi-calendar return content, and that events are included. It omits output format details, but that is minor for a no-argument read 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?

Two tight sentences: the first enumerates what is returned, the second front-loads the routing rule. No redundant restatement of the title or name.

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 zero-argument, read-only lookup tool with no output schema, the description covers the calendars, timezone, weekday, zodiac and events, which is everything an agent needs to call and interpret it. Nothing material is missing.

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 zero parameters, so there is nothing for the description to disambiguate, and the baseline is a 4. The mention of Tehran time usefully clarifies the implicit timezone context even though no parameter exists.

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 specific verb and resource — getting today's date across Jalali, Gregorian and Hijri calendars — plus Tehran time, weekday, zodiac sign and events. It is clearly distinguishable from siblings like ti_convert_date and ti_month, which operate on other dates rather than '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 explicitly says to use this first for "today", "now" or the date/time in Iran, giving a clear selection rule versus conversion or month-listing siblings. It stops short of naming an explicit alternative or stating when not to use it.

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