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

Annotations already declare readOnlyHint, idempotentHint and non-destructive, so the safety profile is covered. The description adds genuine domain behavior beyond that — Smarta vs Vaishnava Ekadashi resolution rules, viddha/arunodaya refusals, Gauna and Vanjuli cases, and parana restricted outside Hari Vasara within Dwadashi — which tells the agent what the output encodes and why some days shift. It does not mention cost/latency, though the 100-credit Tier 4 metadata block does.

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?

The tool's job is front-loaded in the first clause, which is good, but the remainder is a single ~90-word sentence of untranslated Sanskrit terminology (viddha, arunodaya, Gauna, Vanjuli mahadwadashi, Hari Vasara) packed with parenthetical exceptions. It is dense rather than wasteful, but the nesting makes it hard to scan and the other five vrat types are never described at all.

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?

An output schema exists and the schema documents 10 parameters at 90% coverage, so the description need not explain return shape. However, for a year-long calendar tool it omits what Pradosh, Sankashti, Purnima, Amavasya and Masik Shivaratri entries contain and how the 'place' plus timezone combine, leaving the non-Ekadashi majority of the output unspecified. The Ekadashi depth is disproportionate to everything else that is left out.

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 90%, so parameters such as year range, types enum, fields compact mode, ayanamsa, timezone resolution and latitude limits are already fully explained in the schema. The description adds no parameter-level meaning beyond what the schema provides; the 'for the place' phrasing merely implies latitude/longitude. Baseline 3 applies when the schema does the heavy lifting.

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 opening clause 'Every vrat of the year for the place' states a specific verb and resource, and the title enumerates the covered vrat types (Ekadashi, Pradosh, Sankashti, Purnima, Amavasya, Masik Shivaratri). It does not distinguish this from nearby calendar siblings such as astroway_vedic_calendar_festivals, astroway_vedic_panchang_tithi or astroway_vedic_calendar_ics, so the boundary is inferred rather than stated.

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 when-to-use or when-not-to-use guidance: nothing says to pick this over the festivals, panchang or ICS calendar tools, and no prerequisites (location needed, sidereal school) are framed as usage conditions. The only hint is the required year/latitude/longitude metadata block, which is structural rather than instructional.

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