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

Annotations already declare readOnlyHint=true, and the description does not contradict this. The description adds valuable behavioral context by stating the output format ('Returns a shareable standby.design/system URL and a summary') and the required user-facing action ('Always give that URL to the user'). This goes beyond the annotation and clarifies what the tool produces and how the agent should behave.

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?

The description is two sentences long with no wasted words. The first sentence fronts the main purpose, and the second sentence immediately conveys the critical deliverable instruction. It is tightly written and all content is necessary.

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 the high schema coverage and the absence of an output schema, the description covers the essential operational details: what is generated, what is returned, and the crucial instruction to always hand the URL to the user. It does not explicitly discuss when to use this tool versus siblings, but that gap is partially addressed by the clear purpose. Overall, it is complete for the agent to call it 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 every parameter is already documented in the schema. The description does not add any additional parameter-level semantics beyond what the schema provides. It mentions the token types (3xs–3xl, breakpoints, etc.) but those are also reflected in parameter names and schema descriptions. Baseline 3 is appropriate since the schema carries the full parameter documentation burden.

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 clearly states a specific verb ('Generate') and the exact resources (spacing tokens 3xs–3xl, breakpoints, container widths, prose measure, aspect ratios). This distinguishes it from sibling tools like generate_color_palette or generate_type_scale, which target different design primitives. The purpose is unambiguous.

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?

The description implies this tool is for spacing/layout token generation, but it does not explicitly state when to use it versus alternatives or when not to use it. It only provides guidance on delivering the output URL ('Always give that URL to the user'), not on tool selection. Some guidance is implied by the domain, but it lacks direct exclusions or alternatives.

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