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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, so the safety profile is covered. The description adds genuinely useful non-schema facts: the 20-credit Tier 2 cost and the Horary grouping. It says nothing about response shape or precision, but the output schema exists so that is not a real gap.

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?

One sentence with the operative scope up front, followed by two compact metadata lines for group and cost. Nothing is redundant and nothing needed is buried behind preamble.

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 15-parameter chart-calculation tool with 4 required birth-data fields and low schema coverage, the description omits any parameter orientation and never explains what the caller must supply. The existence of an output schema absolves it of describing return values, but it is under-specified for the inputs an agent must construct.

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 only 33% across 15 parameters, so the description carries a real compensation burden and provides none: no hint that date, time, latitude and longitude are required, no mention of chart-configuration options like zodiacType, houseSystem or ayanamsa. An agent gets no guidance beyond the raw schema for the two-thirds of parameters that are undocumented.

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 plus resource ('List all aspects the Moon will make') and bounds the scope precisely with 'before leaving its sign'. That scope clause distinguishes it from the nearby Moon-focused siblings (astroway_horary_moon_voc, astroway_calendar_moon_aspects) without needing to open 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?

The phrase 'the key timing tool in horary' signals the domain and intent, implying when to reach for it. However, it names no alternative and gives no when-not condition, so an agent choosing between this and astroway_horary_moon_voc or astroway_horary_horary must infer the boundary itself.

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