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

Annotations cover the safety profile (readOnlyHint=false, destructiveHint=false, idempotentHint=false, openWorldHint=true), and the description adds real behavioral context: deterministic mulberry32 RNG when seed is passed, daily seed when omitted, and upright-only cards via allowReversed=false. It also surfaces the 100-credit cost. It does not explain what the rendered output looks like or delivery method, but the output schema covers returns.

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?

Three tight sentences, front-loaded with the default spread and then the option inventory. No filler; each sentence carries usable parameter information.

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?

For an 8-parameter report tool with a nested whitelabel branding object and five non-schema-documented parameters, coverage is partial. The output schema removes any need to describe return values, but an agent gets no help on language, whitelabel, or compact-mode parameters.

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 coverage is only 25%, so the description must compensate, and it does for the most consequential parameter: it enumerates all ten spread values even though the schema only carries maxLength=64 with no enum. It also explains seed and allowReversed semantics. It says nothing about name, language, fields, precision, or whitelabel, leaving four parameters undocumented.

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: 'Render a tarot reading PDF', and the title adds the HTML variant. This distinguishes it from the draw-only siblings (astroway_tarot_rider_waite_draw_three_card) and other report generators, though it never explicitly names an alternative.

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?

Gives defaults (three-card spread, daily seed) but no when-to-use/when-not guidance and no routing to alternatives such as the draw tools or astroway_reports_generate. The agent must infer that this is the PDF-rendering path rather than the card-drawing path.

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