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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds the cost tier (10 credits, Tier 1), which is useful, but omits the significant behavioral fact that the body accepts either raw birth data or two precomputed charts (the latter at 1 credit), a distinction the schema alone carries.

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?

Two tight sentences plus bracketed metadata, with the layout description front-loaded and no filler. The metadata tags are terse and scannable, though they carry cost/group rather than task-relevant guidance.

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?

This is a complex tool with two distinct input modes, a cost difference between them, and a format option defaulting to json despite the 'Bi-Wheel (SVG)' title. The description says none of this, so an agent reading only the description could easily send the wrong body shape or expect SVG output by default.

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 a middling 67%, and the description contributes nothing about the three top-level parameters (body, fields, precision) or the dual-mode body union. It neither explains the birth-data vs precomputed-chart choice nor mentions compact mode, leaving the schema to do all the work with a real gap remaining.

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 and resource ('Two concentric wheels: inner natal + outer ring with transit (or progression) planets') and identifies the layout convention. It does not, however, differentiate itself from close siblings such as astroway_render_tri_wheel, astroway_render_composite, or astroway_render_wheel_western, which an agent must choose between.

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 parenthetical '(or progression)' hints at the comparison being drawn, but there is no statement of when to pick this over tri-wheel, composite, or a single western wheel, and no prerequisites or exclusions. An agent gets no routing guidance from the description.

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