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

Annotations already declare readOnlyHint=true, idempotentHint=true, and closed-world, so the safety profile is fully covered structurally. The description's contribution is domain semantics (what a progression is) rather than behavior — it says nothing about what a result contains, how houses/angles are affected when time is omitted, or precision limits.

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?

A single tight sentence with the core concept front-loaded and the two methods defined inline; nothing is wasted. It loses a point only because the sentence fragment lacks an action verb, making the opening slightly less directive.

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 7-parameter tool with no output schema, the description does not indicate what is returned (planet positions, angles, house cusps?) or how results relate to the natal chart it presumably derives from. The schema compensates for input guidance, leaving the output expectations largely unexplained.

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 every parameter including the method enum and the noon-fallback caveat is already documented in the schema. The description adds only the conceptual meaning of the progression methods, which mildly reinforces the 'method' parameter but names no parameter explicitly.

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?

It names a specific resource — the progressed chart as of today — and distinguishes its two computation modes (secondary progressions vs. solar arc directions) with parenthetical definitions. However, it reads as a noun phrase with no verb and never explicitly contrasts itself with natal_chart or transits, so the agent must infer the boundary from domain knowledge.

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 'as of today' framing implies when the tool applies, and it explains what each of the two methods means, but it never says when to prefer secondary progressions over solar arc, nor when to reach for this instead of the sibling transits or returns tools. Usage is implied rather than stated.

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