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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, so the safety profile is covered. The description adds genuinely non-structured behavior: the response always states the city, time zone and date actually used, and the tool will actively ask for a city when neither the parameter nor an approximate location is available. That interactive fallback is behavior an agent could not infer from the schema alone.

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?

Front-loaded with purpose, then contents, then edge-case behavior — no wasted sentences. 'Always states the city, time zone and date used' borders on restating return values that an output schema already covers, a minor redundancy.

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?

With an output schema present, the description does not need to document return shape, and it still characterizes the payload at a high level. Together with full schema coverage of both optional parameters and the missing-city fallback, an agent has everything needed to call it correctly.

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 100% and both parameters already carry their own descriptions (fixed city list, ISO date format, today default, approximate-location fallback). The description restates the city fallback but adds no format or semantic detail beyond the schema, so the baseline 3 is correct.

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 the resource (Panchang for one day in one city) and enumerates the exact contents: sunrise/sunset, moonrise/moonset, tithi with paksha, nakshatra, yoga, karana with end times, plus that day's festival. This makes it clearly a single-day almanac tool rather than a festival-lookup or vrat-guide tool. It never names get_festival_dates or get_vrat_guide to draw the boundary explicitly, so it falls just short of a 5.

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?

Usage is implied rather than stated: the 'one day in one city' framing and the note about asking for a city when none is available tell the agent how the call behaves, but there is no explicit when-to-use-this-vs-get_festival_dates/get_vrat_guide guidance. Defaults for city (approximate location) and date (today) are covered in the schema rather than the description.

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