Cosmogram: Hamburg School 90° dial (SVG)

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

Annotations already cover read-only, idempotent, non-destructive and closed-world, so safety needs no restating. The description adds a behavioral fact beyond the schema — a 10-credit Tier 1 cost and the POST endpoint — which is genuinely useful for an agent budgeting calls. It stops short of warning that the render defaults to JSON rather than SVG, which is the main behavioral surprise here.

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 sentences of substance plus tag lines, front-loaded with the technique and the plotting rule. Nothing is redundant, though the brevity shades into under-specification given the rich options the schema exposes.

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 annotations cover safety. However, for a renderer with fourteen option fields and a json-versus-svg format default, an agent would benefit from one line saying it produces an image and that format must be set to svg to get one. That gap keeps it at minimum-viable.

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% and the single parameter is a deeply documented birth-data body, so the schema carries all the semantics. The description contributes no parameter detail at all — notably nothing about the cosmogram flag, the format enum defaulting to json, or the theme option. Baseline 3 for high coverage with no added value is correct.

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 names a specific technique (cosmobiology 90° dial) and states the visual output precisely: planets plotted at longitude mod 90 across four quadrants with Cardinal/Fixed/Mutable repeated. That distinguishes it from the calculation sibling astroway_cosmobiology_dial_90 and the other wheel renderers well enough for an agent to pick it. It is slightly weakened by never stating the output is an SVG image in the description text itself (only the title carries that).

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?

There is no when-to-use guidance: nothing says to use this when the user wants a picture rather than the numeric dial data from astroway_cosmobiology_dial_90, and nothing points to astroway_render_wheel_western for ordinary charts. The agent must infer selection from the name and the shared 90° vocabulary.

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