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

Beyond the readOnly/idempotent annotations, it discloses meaningful behavior: results are computed from birth date and town, an omitted birth_time can make the answer vary across the birth day, and in that case each possibility is returned with the hours it holds for. That is exactly the ambiguity an agent needs to anticipate before calling.

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 core usage trigger and the parameter-routing instruction are front-loaded, and the return-value sentence follows. It is dense with parenthetical examples but each clause maps to a distinct fact (trigger, enum, return fields, birth-time caveat), so little is wasted.

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 no output schema, the description carries the return burden and does so adequately: all seven karakas in order with sign, degree, nakshatra, navamsa sign, and house when a birth time is given. Combined with the birth-time caveat and the two required parameters, nothing essential 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 coverage is 100%, so the baseline is 3, and the description still adds value by tying the 'which' enum to the specific karaka asked about and explaining why birth_time precision changes the output. It does not add format/detail beyond the schema for birth_date or birth_place, so it sits above baseline but not maximally.

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 description names the exact deliverables (atmakaraka, amatyakaraka, darakaraka, and all seven chara karakas) in Jaimini/Vedic astrology, distinguishing it from siblings like divisional_chart or vedic_birth_chart that serve different chart needs. An agent can identify the verb+resource without opening any schema.

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?

It explicitly frames when to trigger ('Use this when someone asks for their...') and supplies literal user phrasings such as 'what is my atmakaraka' and 'darakaraka in navamsa', plus the routing rule to set 'which'. It stops short of naming a sibling alternative for a competing case, so it is clear context rather than full when/when-not guidance.

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