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 real behavioral value beyond that: it says what is returned (the running cycle of 9 mahadashas), that timing is anchored to the initial-balance-adjusted birth time, and the 20-credit Tier 2 cost. Rate limits and pagination behavior are not mentioned.

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-loads the definition, then the calculation rule, then the use case, then the return shape. The period list ("Ketu 7/3, Venus 20/3, Sun 2, Moon 10/3, etc.") is informative but trails into an incomplete enumeration that a table or single multiplier statement would have covered more cleanly.

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, so return values need no prose explanation, and the description still adds the semantic anchor (initial-balance-adjusted birth time). The only real gap is the absence of any hint that full birth data (date, time, coordinates, timezone) is required, though the phrase "chart's... birth time" implies it.

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%, with the nested birth-data object, timezone/ayanamsa rules, and compact-mode fields and precision all documented in the schema itself. The description contributes nothing about parameters, so the baseline 3 applies rather than a penalty or a bonus.

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?

States a specific verb/resource (returns the mahadasha cycle) and pins the variant precisely: a 1/3-scale Vimshottari with the same 9-planet sequence and nakshatra rule, distinguishing it from astroway_vedic_dashas_vimshottari_maha without naming it. The 40-year cycle and the explicit period arithmetic make the tool's identity unmistakable among the many dasha siblings.

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?

Gives a clear positive condition: "Useful when finer-grain timing is needed within a Vimshottari-equivalent span." It does not state when NOT to use it or point at the alternative sibling (e.g. standard Vimshottari for conventional periods, or tribhagi_antar for sub-levels), so an agent must infer the routing itself.

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