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

Annotations already declare readOnlyHint=true and openWorldHint=false; the description is consistent with that by framing the operation as generation and returning a URL/summary. It adds useful behavioral context beyond annotations, such as the deliverable being the shareable URL and the instruction to always give that URL to the user, plus the exact output composition. No contradiction found.

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?

Every sentence earns its place: scope, output breakdown, workflow, deliverable emphasis, and routing to alternatives. It is detailed but tightly structured, with no filler or repeated boilerplate.

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?

Given four optional parameters with 100% schema coverage, no output schema, and annotations covering safety, the description is complete for invocation. It states what is returned, what the deliverable is, which code exports are handled elsewhere, and how to start, making it sufficient for an agent to select and call 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 100%, so the baseline is 3. The description raises this slightly by mapping the axes to experience ('energy ... sets the tempo', 'material ... sets how much spatial motion overshoots') and by prescribing the parameter relationship: 'Start from a preset, then fine-tune with energy/material.' These are meaningful, though partially redundant with the rich schema descriptions.

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 opens with a specific verb and resource: 'Generate spring-based motion tokens' from two named axes. It enumerates exact outputs (6 primitive springs, 11 semantic tokens, reduced-motion rule), which clearly distinguishes it from the color/icon/shape/space/type generator siblings and from export_design_system.

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?

It gives an explicit workflow: 'Start from a preset, then fine-tune with energy/material.' It also names an alternative and the condition for using it: 'Use export_design_system for CSS, design tokens or the LLM briefing; SwiftUI, Compose and Motion (JS) code is exported in the UI at standby.design/motion.' This tells the agent when not to use this tool.

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