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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so credit is due for the additions: server-side rendering with no browser and a 10-credit Tier 1 cost. However, it omits notable behaviors such as the two input modes with different costs (birth data at 10 credits vs. a pre-computed chart object at 1 credit) and the fact that 'format' defaults to json rather than the SVG the description advertises.

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, front-loaded sentences with no filler, plus compact Group and Cost tags that are genuinely useful metadata. Everything present earns its place, though it is arguably too terse for the tool's complexity.

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?

The output schema and annotations relieve the description of return-format and safety disclosure, and it does state what is drawn and that rendering is server-side. It is nonetheless thin for a tool whose body supports two structurally different input modes (birth data vs. a pre-existing chart) that the description never hints at.

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?

The description contributes zero information about any of the three parameters, despite schema description coverage sitting at only 67%. It neither clarifies the body/fields/precision roles nor compensates for the undocumented third of the schema, so the schema carries the entire burden.

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 specific verb (Render) and resource (a Western natal wheel as SVG) plus the concrete content it draws: signs ring, houses ring, planets, aspect lines. The 'Western' qualifier implicitly separates it from the Vedic wheel siblings, but it never names or contrasts against other Western renderers such as bi_wheel, tri_wheel, or composite.

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 description gives no when-to-use guidance and names no alternatives, even though the sibling list contains several closely competing renderers (bi_wheel, tri_wheel, composite, cosmogram, aspect_grid). 'Pure server-side, no browser needed' is an environment note, not a routing rule.

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