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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds genuinely useful behavior beyond that: the no-argument default returns all 63 rules as one line, detail='full' yields complete text including how to detect violations in code, and rule texts are in German. The German-language caveat is a meaningful non-obvious trait.

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?

Dense but front-loaded: purpose first, then the tokens-vs-rules distinction, then call timing, then the no-args behavior and detail semantics. Every sentence carries information; only the repeated category enumeration (also in the schema) is slightly redundant.

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?

There is no output schema, so the description must explain the return shape, and it does: default all-rules-as-one-line, full text under detail='full', language of the text. Combined with the covered annotations and full schema coverage, an agent has everything needed to call this 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 adds value beyond the schema by explaining what the two detail levels actually produce ('one line' vs 'complete text including how to detect violations in code'), enumerating the categories, and clarifying the summary-vs-full default interaction.

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 (returns design rules for building UI with design tokens) and explicitly distinguishes itself from the token tools: 'The tokens say which values exist; these rules say how to use them.' An agent knows exactly what this returns and how it differs from get_design_system or the generate_* token 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?

Gives a clear trigger: 'Call this before building or reviewing views.' It also implies the boundary with token tools via the tokens-vs-rules sentence. It stops short of naming a specific sibling tool or stating when NOT to call it, so it is strong but not fully exhaustive.

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