Update global styles

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

Annotations mark this as a write operation (readOnlyHint false) but say nothing about merge behavior or immediacy. The description adds crucial behavioral context: changes apply site-wide immediately, and partial settings replace the entire branch. This goes beyond the annotations and helps the agent predict side effects, though it doesn't cover authentication, rate limits, or reversibility.

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?

Three short, front-loaded sentences: the first states the purpose, the second the immediate effect, and the third the critical usage caution. No fluff, every sentence earns its place, and the most important caveat is highlighted in a warning-like manner.

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 tool with 3 optional parameters and nested open-world objects, the description covers the essential context: what is updated, the immediate site-wide impact, and the merge/replace caution. It guides the agent to read first, which is critical for safe usage. No output schema means return values need no explanation; nothing an agent needs to call this correctly is missing.

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 100% schema coverage, the baseline is 3, but the description adds real semantic value for the `settings` parameter by explaining the merge behavior ('partial settings replaces that whole branch'). This clarifies a non-obvious aspect not present in the schema. The styles and site_id parameters are already well documented in the schema, so the description doesn't need to repeat them.

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 states the verb 'Update', the resource 'a block theme's global styles', and enumerates what that includes (palette, typography, spacing, per-block styling). This clearly distinguishes it from the sibling `get_global_styles` and other update tools, making the purpose unmistakable.

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 explicitly advises 'Read them first' and explains the merge semantics ('a partial settings object replaces that whole branch'), which guides when and how to use the tool safely. It also hints at the alternate `get_global_styles` by telling the user to read first, though it doesn't name the sibling or provide explicit exclusion conditions. The site_id parameter guidance in the schema also supports usage decisions.

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