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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds meaningful behavior beyond that: it requires a signed-in user, is bound to a saved chart, is capped at 31 days on free accounts versus up to a year on paid plans, and computes via Swiss Ephemeris. It does not say what happens if the requested days exceed the plan cap, which is the one notable omission.

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 core content is front-loaded in the opening clause, and the density of facts (phases, strength, tone, plan limits) means little is wasted. The sentence is long and dash-heavy, and the fragment 'a few sentences on what each transit is about' reads as a dangling list item, so structure is good but not airtight.

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?

There is no output schema, so the description must carry return semantics — and it does, describing each transit entry's phases, exactness to the minute, retrograde passes, strength rating, tone, and interpretive text. It also discloses plan-based range limits and the ephemeris source. What remains unstated is error behavior when limits are exceeded, a minor gap for a read-only tool.

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% and each of the four parameters (days, lang, chart_id, current_timezone) is documented in the schema. The description only echoes a few of them implicitly — 'in the given time zone' for current_timezone, 'one saved chart' for chart_id, '31 days' for days — without adding format or precedence rules. Baseline 3 is appropriate when the schema carries the load.

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 names a concrete resource (the personal transit calendar of one saved chart for the signed-in user) and enumerates its contents: Sun–Pluto transits to natal planets/Asc/MC, three phases, retrograde passes, strength, tone, and interpretation. That is far more specific than a restatement of the name. It stops short of naming a sibling it is not (e.g. my_transits or transits_today), so an agent must infer the boundary between the personal calendar view and plain transit lookups.

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?

Example questions — «when is my peak this month?», «what is coming in December?» — give clear situational context for when this tool fits. The account-tier limits (31 days free, up to a year on paid) further bound its use. No explicit when-not guidance or named alternative is given, which keeps it below a 5.

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