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

Annotations already declare readOnly/idempotent/non-destructive, so the description earns credit for the extra context it supplies: the 3-level cascade it performs (MD → AD → 9 PDs) and the Tier 2 cost of 20 credits. It does not disclose what happens when no target date is supplied (does it default to now?), which is the main remaining behavioral gap.

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 tightly written sentences with the definition first and the computation second, plus two structured metadata tags. No filler, no repetition of schema or annotation content.

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?

Output schema exists so return values need no prose; parameters are fully documented in the schema; annotations cover the safety profile. The description contributes the one thing structured fields cannot — what the tool actually computes and what it costs.

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% — body, fields and precision are all documented in the schema, including the timezone/ayanamsa/houseSystem rules. The description adds no parameter-level meaning (e.g. how targetDate interacts with 'the running' period), so the baseline 3 applies.

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 pair ('return 9 PDs of that AD') and defines the exact period level — pratyantardasha nested inside the running antardasha. That is enough to place it among the five Vimshottari levels, but it never explicitly contrasts itself with vimshottari_antar, prana or sookshma siblings, so the agent must infer the hierarchy position from the name alone.

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: 'within the running Antardasha' tells the agent the tool is for the third tier of the currently active period, but there is no explicit when-to-use, when-not-to-use, or named alternative (e.g. use _antar for the second level). Minimum viable guidance for a level-selector tool.

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