Star Map (SVG)

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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds genuine value with the projection type and magnitude scaling, plus endpoint and credit cost, which annotations do not convey. It omits operational details that matter here: the format option defaults to 'json' (despite the 'SVG' title), the 2000-point cap, and the size/theme rendering controls.

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, front-loaded with the operation and behavior, with no wasted prose. The bracketed metadata lines (group, endpoint, required, cost) are terse and useful rather than filler.

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 the projection behavior is stated. However, for a 6-parameter tool with nested objects and 0% schema coverage, the description leaves too much undescribed — the geographic/zenith parameters and theme/format options are unexplained, and the json-vs-SVG default ambiguity is not resolved.

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 0%, so the description must carry parameter meaning and it only partially does: it clarifies that points are RA/Dec coordinates with a magnitude field feeding brightness scaling. It says nothing about observerLatDeg, zenithDecDeg, capAltitudeDeg, or the options object (size, theme, format, showAspects, showRetrograde), leaving five of six parameters with no semantic guidance anywhere.

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 ('stereographic projection of caller-supplied points (RA/Dec)') and names two concrete behaviors it handles (brightness magnitude scaling, labels). The resource is clearly distinct from render siblings like render_wheel_western or render_aspect_grid, though no sibling is named explicitly to sharpen the boundary.

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 statement of when to choose this star map over the many other render_* tools (cosmogram, aspect_grid, parans_star, wheel_western) or when not to use it. 'Required: points' signals a precondition but not a usage policy, so the agent must infer selection from the name alone.

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