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

Annotations already establish read-only, idempotent, non-destructive and closed-world, so the description is free to add real value and does: exact ephemeris convention, mean node for Rahu, which chart elements are produced, and the data-handling guarantee that birth data is neither stored nor logged. That privacy statement is behavior an agent cannot get from any structured field.

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 verb and resource, and the two trailing sentences carry distinct jobs (usage triggers, scope limit, data handling). The first sentence is a long enumerated run-on, but each item in the enumeration is informative output content, 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?

There is no output schema, yet the description enumerates the returned chart contents (rashi, degree, house per graha, nakshatra/pada/lord, Moon's nakshatra symbol and deity), which is exactly what an agent needs to know before calling. Input edge cases like unknown birth time are covered by the schema.

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 all seven parameters (including the birth_time-omission consequence and place/coordinates fallback) are already documented in the schema. The description adds no extra parameter guidance beyond 'birth data', which is the correct baseline-3 outcome when the schema does the work.

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?

Specific verb ('Calculates') plus a precisely bounded resource ('Vedic (Jyotish) birth chart') with the computational basis named (Swiss Ephemeris, Lahiri ayanamsa, whole-sign houses). The scope line 'Pure calculation: no doshas, yogas or predictions' separates it from the sibling dasha/prediction tools and from natal_chart's likely tropical output.

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 concrete user-question triggers ('what is my nakshatra', 'my Vedic chart', 'my rashi / Moon sign in Jyotish') and a clear exclusion ('no doshas, yogas or predictions'). It does not name the sibling that handles those excluded cases (e.g., vimshottari_dasha), so the routing is implied rather than explicit.

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