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 covered. The description adds genuinely non-annotation context: the POST endpoint and the '[Cost: 20 credits (Tier 2)]' pricing, which is useful for budget-aware planning. It says nothing about auth or result payload, but the output schema exists.

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 one-sentence purpose is front-loaded and the bracketed metadata lines are scannable and compact. The endpoint line is close to redundant given the tool-name-to-route mapping, but nothing is bloated.

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?

Output values need not be described because an output schema exists, and annotations cover safety. However, for a 15-parameter natal-chart calculation, the description never explains how the natal reference is supplied or what the defaults (tropical vs sidereal, house system) mean, leaving a meaningful gap against the 33% parameter coverage.

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% (fields, ayanamsa, timezone, precision, timezoneOffset are documented; zodiacType, houseSystem, cosmogram, ayanamsaId, city, name, date, time, latitude, longitude are not). At this low coverage the description is expected to compensate, yet it only repeats the four required parameter names, adding no meaning beyond the schema's own required array.

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 (antiscia and contra-antiscia) and even defines the technique parenthetically as mirror points along the Cancer/Capricorn axis, which conceptually separates it from neighbours like midpoints or parallel_aspects. It does not name an alternative sibling explicitly, so it stops short of a 5.

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 and no comparison to sibling techniques such as astroway_aspects_midpoints or astroway_aspects_parallel_aspects. The only contextual aid is the bracketed '[Required: date, time, latitude, longitude]', which restates the schema's required list rather than telling the agent when this tool is the right choice.

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