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

Annotations already declare readOnly/idempotent/destructive=false, so the safety profile is covered. The description adds genuinely useful operational context (endpoint, 10-credit Tier 1 cost, required inputs), but says nothing about output format or that the schema's format field defaults to json despite the 'SVG' title.

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?

Front-loaded with the core sentence, then structured bracketed metadata (group, endpoint, required, cost) that an agent can scan quickly. No wasted prose; only the bracketed cost/endpoint lines are non-essential.

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 render tool backed by a detailed nested schema, existing output schema, and full annotations, the description supplies the remaining essentials: what it draws, the wheel mapping, required inputs, and cost. Complete enough to invoke correctly.

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?

With 83% schema coverage the schema does most of the work, but the description adds real meaning by mapping the abstract param names: middle = progressed, outer = transit, and natal = natal. That mapping is not derivable from the schema property names alone.

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 concrete verb+resource (renders a tri-wheel) and specifies composition: 'Three concentric wheels: natal + progressed + transit.' It naturally distinguishes itself from two-wheel/cosmogram siblings via 'three concentric' and 'advanced forecasting,' though it never names a sibling explicitly.

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?

'Used for advanced forecasting visuals' implies a use context but gives no when-to-use, no when-not-to-use, and no pointer to alternatives like astroway_render_bi_wheel or astroway_render_wheel_western. Adequate minimum, clear gap.

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