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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered and the bar is lower. The description adds the cost (20 credits, Tier 2), the POST endpoint, and the arithmetic used to derive each sub-period — real added context, though the group/endpoint lines are boilerplate. It does not state response volume (9 periods) mapping to output, but an output schema exists.

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 tool's identity and scope in one sentence, followed by a compact formula and the standard metadata block. No filler prose; the only mild excess is the metadata block that repeats across the whole tool family.

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 need not explain return values, and the rich body schema covers inputs including timezone and ayanamsa handling. What remains thin is routing: no explicit contrast among the five Tribhagi levels (maha/antar/pratyantar/prana/sookshma) that share nearly identical names in the sibling list.

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 body (birth data, timezone semantics, house system letters, offsets) is already fully documented in the schema and the nested body description. The description only references `targetDate`, which the schema already defines with its pattern, adding no new syntax or semantics; 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: it computes the Tribhagi Antardasha, defined as the 9 sub-periods of the running Mahadasha at targetDate, plus the proportional-split formula. This implicitly separates it from tribhagi_maha (the parent level) and the deeper tribhagi_pratyantar/prana/sookshma levels, but it never names those siblings or the hierarchy explicitly, so an agent must infer the distinctness.

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 by the definition — you call it when you want the second-level (antardasha) division of the current Mahadasha at a given target date. There is no explicit statement of when to prefer this over the sibling tribhagi levels or the other dasha systems (vimshottari, yogini, etc.), and no prerequisites beyond the schema-required birth data.

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