preview_card_template

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered. The description adds that the call substitutes text and returns 'the template structure including page layouts', which tells the agent the response shape in the absence of an output schema — genuinely useful behavioral context.

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 with the action front-loaded, the usage cue second, and the return value last. No filler or restatement of the tool name, though the return-value sentence slightly overlaps the usage sentence.

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 a read-only preview tool with six fully documented parameters, the description covers purpose, substitution intent, and return content. The absence of an output schema is partly compensated by naming the returned structure, though nothing is said about rendering cost, rate limits, or invalid-UUID handling.

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 every parameter including the placeholder-substitution fields and variation_uuids is already documented in the schema. The description only gestures at 'couple's names and wedding date' and adds no syntax, format, or default details beyond what the schema provides, so the baseline 3 applies.

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 states a specific verb (render/preview) and resource (invitation template) and adds the key qualifier 'with text substituted in', which separates it from pure metadata tools like get_card_suite. It is not explicitly differentiated from the other preview tool (preview_qrcode), but the resource noun is distinctive enough that an agent can route correctly.

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?

'Use to see how a design would look with your couple's names and wedding date' gives implied usage context, which is more than nothing. However, it names no alternatives and sets no conditions for when-not to use it versus swap_card_project_variation or get_card_suite, leaving the agent to infer the boundary.

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