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

Annotations already cover read-only/idempotent/non-destructive, and the description adds genuinely new context: Swiss Ephemeris computation, no forecast text generated, and an explicit privacy guarantee that birth data is not stored or logged. What it doesn't clarify is output shape or how an omitted birth_time degrades the result (that detail lives only in 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?

Four sentences, front-loaded with the computed content, then usage, then defaults, then provenance/privacy – a sensible order with little waste. Slightly dense in the first sentence (planet list plus orbs) but the density is substantive, not filler.

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 10-parameter tool with no output schema, the description adequately implies the return contents (tight aspects with orbs, each planet's sign and natal house, Moon phase). It stops short of stating what is omitted when birth_time or place are absent, leaving that to the schema, but nothing essential for correct invocation is missing.

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 every parameter, including the orb-relevant defaults, enums and coordinate/timezone lookups. The description echoes the date-default behavior ('today in the person's time zone') but adds no syntax, precedence or edge-case guidance beyond the schema, so 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?

The description states a specific verb ('Lists') and a precisely scoped resource: tight transits of a given day to a natal chart, enumerating the bodies (Moon, Sun, Mercury, Venus, Mars, Jupiter, Saturn), the natal points (planets, Ascendant, MC) and the exact orbs (2°, 3° for Jupiter/Saturn). That scoping separates it from natal_chart (birth chart) and sky_today (general sky) without needing to name 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?

It gives explicit usage examples ('what are my transits today', 'what is happening in my chart this week') and the date-default rule, which tells an agent when to reach for it. It does not explicitly exclude cases or point to a sibling like sky_today when the user wants a general sky rather than a natal-based reading.

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