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

Annotations already declare this a safe, idempotent, closed-world read, so the safety profile needs no restating; the description adds useful non-annotation context in the form of the 10-credit Tier 1 cost and the magnitude-scaling/label behavior. However, it omits a behavioral trap: the tool is titled SVG but the schema default format is json, and nothing here warns the agent to pass format explicitly.

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 sentences plus bracketed group/cost tags, with the core capability front-loaded. No filler or repetition; the only mild overhead is the boilerplate metadata lines.

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 described, but for an 8-parameter tool with a nested options object and projection geometry, the description leaves most inputs unexplained. The 25% schema coverage is not offset, leaving an agent without enough grounding to use the projection and rendering options 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?

Schema description coverage is only 25% across 8 parameters, so the description is expected to compensate and largely does not. It hints at points (raDeg/decDeg), magnitude and name/labels, but says nothing about the projection parameters (observerLatDeg, zenithDecDeg, capAltitudeDeg), precision, fields, or the nested options block (size, theme, showAspects, showRetrograde).

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 rendering capability — a stereographic projection of caller-supplied RA/Dec points with magnitude scaling and labels — which clearly separates it from the chart-driven siblings (render_wheel_western, render_bi_wheel, etc.) that take computed chart data. The SVG output itself is only implied by the title, not the description, so it is not a flawless 5.

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 reach for this tool versus the many other render_* siblings, no prerequisites, and no exclusions. The only non-purpose text is the group/cost metadata, which does not help an agent decide whether this or render_cosmogram, render_wheel_western, or render_aspect_grid is correct.

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