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

Beyond the read-only and idempotent annotations, it discloses the astronomy engine, tropical/geocentric frame, null behavior for missing time, and the noon-estimate caveat for the Moon. This is exactly the behavioral context an agent needs and none of it contradicts the annotations.

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 description is dense and front-loaded with output contents, then caveats. The closing HTTP-endpoint sentence is mildly redundant for tool selection, but the rest earns its place; it stays within a few sentences and follows a logical structure.

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 complex astrology endpoint with no output schema, it enumerates the return components, required inputs, optional behavior, and astronomical frame. The null-time caveat and Moon estimate close the main operational gaps an agent would face.

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 already 100%, and the description adds meaningful semantics: lat/lng/tz are tied to angles and houses, time is optional with explicit null behavior, and no noon is substituted. This is more than the schema alone communicates.

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?

Description opens with a precise inventory of what the tool returns (ten planets, houses, angles, nodes, aspects) and explicitly frames it as the Western natal chart endpoint, distinguishing it from the Eastern bazi/numerology siblings. The phrase 'This is the one endpoint that requires lat, lng and tz' further disambiguates it.

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?

The description clearly signals when to use it ('requires lat, lng and tz') and gives explicit behavior for omitted time (null angles/houses rather than noon substitution). It does not name sibling alternatives or state when not to use them, but the location-based condition effectively routes an agent.

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