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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is fully covered. The description adds the credit cost (20 credits, Tier 2) and the endpoint, which is useful operational context, but nothing about latency, auth, or the difference between built-in and custom lots.

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?

Two sentences front-load the purpose and the return content, followed by compact bracketed metadata for group, endpoint, and cost. No wasted prose, though the metadata lines are boilerplate rather than descriptive.

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, return values need no explanation, and the 100%-covered input schema handles all parameter detail. Annotations carry the safety profile, so the remaining gap is only the lack of alternative-tool routing, which is minor for a single-purpose calculation endpoint.

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, fields, and precision parameters are already fully documented in the schema. The phrase 'and any custom formula' loosely gestures at the parts array, but adds no syntax or constraint detail beyond what the schema already provides; 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 (Calculate) and resource (Arabic parts / Lots) and the input context (a natal chart), plus what is returned (positions for standard lots such as Fortune and Spirit). It is clearly distinct from the many rendering/calendar siblings, though it never explicitly contrasts itself with any of them.

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?

There is no when-to-use guidance, no mention of prerequisites beyond 'from a natal chart', and no naming of alternatives or when this should be preferred over other points/aspects tools. Usage must be inferred entirely from the tool name and group tag.

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