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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered. The description adds the credit cost (10, Tier 1) and group tag, which is genuinely useful pre-call context, but says nothing about the surprising json default when the title advertises SVG.

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 short sentences, purpose front-loaded, with cost/group metadata clearly bracketed at the end. No wasted prose, though the bracket tags sit slightly awkwardly inside a description field.

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?

An output schema exists so return values need not be explained, and cost is disclosed. However, for a rendering tool with a large nested options object the description never resolves the json-vs-svg default tension implied by the SVG title, nor routes the agent among the many sibling render tools.

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 the nested chart1/chart2 and options fields are already documented in the schema. The description adds no parameter-level meaning beyond that, which is the expected baseline when the schema carries the 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+resource: computes a midpoint composite from two natal inputs and renders it as a Western wheel. This is clear enough to separate it from siblings like astroway_render_bi_wheel or astroway_horoscope_compatibility, but it never names those alternatives explicitly, so the differentiation is inferential rather than stated.

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?

No when-to-use guidance at all. The schema mentions synastry/composite/davison as a family, yet the description does not say when a composite is the right choice versus a synastry or davison chart, nor when to prefer astroway_render_wheel_western for a single chart.

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