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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety is covered. The description adds genuinely non-structured traits: cost (1 credit), the fact that only successful calls are charged, a free sandbox key returning fixed sample data, and an explicit determinism guarantee. The half-filled-location refusal rule is useful but largely duplicates the schema.

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 body is dense and front-loaded, with cost and determinism called out before the example. The opening fragment 'Natal chart.' merely restates the title and earns little, but the remaining sentences are compact and information-rich.

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?

For a read-only computation tool with a full output schema, the agent needs to know what is computed, what the optional flags change, cost, and determinism — all present. Return-value detail is correctly delegated to the output schema, and the example args make the call shape unambiguous.

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 schema already documents all four parameters, setting a baseline of 3. The concrete example argument object demonstrates the nested birthData shape and correct timezone/coordinate formatting, which adds real value beyond the schema's per-field text.

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 states a specific resource and enumerates exactly what is computed: sidereal (Lahiri) ascendant, nine grahas, twelve houses, yogas, and Vimśottarī daśā, plus optional Western and astrocartography blocks. That is far more specific than the title 'Natal chart'. It never names a sibling (e.g. get_dasha for daśā-only or get_compatibility for synastry), so full sibling differentiation is missing.

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?

Conditional behavior is spelled out well (`western` false omits the Western block, `location` adds astrocartography), which implies when each option applies. However, there is no explicit routing guidance against the many siblings — an agent is left to infer that get_dasha should be used when only daśā periods are needed, or get_compatibility for relationship work.

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