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

Annotations already declare readOnly/idempotent/non-destructive, so safety needs no restating. The description adds genuinely extra behavior: the panchanga day is defined as sunrise-to-next-sunrise, each element carries ISO start/end times and kshaya/vriddhi flags, and the supported date range is 1800-2099. It stops short of auth/rate-limit or pagination notes, keeping it at a solid 4.

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 the core purpose and organized into labeled sections (WORKFLOW, INPUT CONTRACT, DO NOT CONFUSE WITH, docs link), so it is easy to scan. The long parenthetical enumeration of every timing (Rahu Kaal, Gulika, Yamaganda, Abhijit, Brahma Muhurta, Durmuhurta, Varjyam...) is somewhat verbose given an output schema exists, but it still aids selection.

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 single-parameter but output-rich tool, the description covers purpose, sibling disambiguation, input constraints, date range, sequencing with geocode/muhurta/festival_calendar, and links to the full output and error contract. Nothing an agent needs to call it correctly 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?

Schema description coverage is 100%, so the baseline is 3. The 'INPUT CONTRACT' restates the date format (YYYY-MM-DD), the IANA timezone requirement and the lat/lon place inputs, which largely duplicates what the nested schema already documents; it adds the supported date range but no new syntax or default behavior.

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?

Specific verb+resource ('Panchanga for one date at a location') followed by an explicit enumeration of the returned limbs (tithi, nakshatra, yoga, karana) and day timings. The 'DO NOT CONFUSE WITH' block distinguishes it from get_yogas, get_panchanga_calendar and get_tamil_panchanga by stating what each of those returns instead.

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?

Provides an explicit workflow (BEFORE: geocode when only a place name; AFTER: get_muhurta and get_festival_calendar for intervals/yearly needs) plus named alternatives with the condition that selects them. An agent knows both when to use this and when to route elsewhere.

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