Delete CSS custom property

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

Goes well beyond the annotations (destructiveHint, idempotentHint): it discloses that dangling references in card styles are left intact and that the browser falls back to an unset variable, notes the underlying call path, and documents both the success and error payload shapes with the fact that errors are returned rather than raised. This is exactly the kind of consequence-level detail an agent needs before a destructive call.

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-loaded with the action and permanence, then clips into labeled Use when / Returns / Errors blocks, so it is easy to scan. The Returns section largely restates the output schema, which is mild redundancy rather than waste.

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 single-parameter destructive tool with annotations plus an output schema, nothing an agent needs is missing: the side effects on referencing styles, the non-throwing error contract, and the precondition (property no longer used) are all present.

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?

One parameter with 100% schema description coverage, so the schema already carries the semantics. The description adds only 'by id,' which duplicates the schema and adds no format or lookup guidance. Baseline 3 is appropriate.

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 with scope: 'Permanently delete one registered CSS custom property by id.' The 'one' and 'by id' constrain the operation, and among siblings it is clearly distinguishable from card_builder_create_css_custom_property, card_builder_update_card, and the general delete_card/delete_style_preset tools.

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?

Explicit 'Use when: removing a custom property that is no longer used by any card style,' and it warns that references are not checked or updated. It does not name a sibling alternative (e.g., update_card or build_styles when a property is still in use), so the routing guidance is clear but not exhaustive.

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