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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds non-obvious behavior beyond that: the call is free, results are scoped by API key presence, the returned style document matches what the web editor stores, and fonts are returned as a side output. Only the exact response shape/pagination is left unstated.

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?

Front-loads the cost ('Free.') and the three result categories, then adds the handoff to save_custom_preset and the fonts note. Dense but every clause carries information; the parenthetical 'source custom, id custom:cp_...' is slightly jargon-heavy but functional.

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?

No output schema exists, so the description must convey returns — and it does describe three preset categories, the style-document format, the id convention, and the fonts collection. Complete enough to invoke correctly; only finer details (ordering, pagination, per-preset fields) remain unstated, which is acceptable for a zero-param read tool.

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?

With zero declared parameters the baseline is 4, and the description adds relevant semantic context by explaining that output contents depend on whether the caller supplies a key. No invented parameters or misleading nomenclature.

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 and resource set: it lists built-in, community-approved, and (key-dependent) custom presets, plus bundled font families. That is clear and more specific than the title. It never mentions the sibling tools list_custom_presets / list_brand_presets, which overlap with the custom/brand preset portion, so the agent has to infer the distinction.

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 real usage context: copy a returned style JSON 'as a starting point for save_custom_preset', and notes that custom presets only appear 'with a key'. It stops short of stating when to prefer this over list_custom_presets or list_brand_presets, so routing among near-duplicate siblings is left implicit.

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