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

Annotations already cover the safety profile (readOnly=false, idempotent=true, destructive=false), yet the description adds substantial operational context: separator color must come from the neighbouring section or the shape becomes invisible, separators are drawn inside this section hugging its edge, height scales down on phones, and 'invert' is silently ignored because vertical orientation derives from the edge. These are real behavioral gotchas not expressible in annotations.

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 purpose, but it is a single dense paragraph packed with nested parentheticals and repeated restraint advice ('use separators sparingly' and 'do not add them unless the user asked') that could be collapsed. The separator guidance, which is a secondary feature, dominates the length relative to the core style update.

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?

Annotations plus an output schema mean the safety profile and return shape are already covered, and the description fills the large remaining gap of the untyped properties object with concrete field lists and design rules. It is nearly complete; what's missing is how merges behave against existing nested styles (e.g. whether a partial background replaces or augments the current one).

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?

The four top-level params are 100% schema-documented, but the required 'properties' object is free-form (additionalProperties: true) with no nested schema, so the description must carry the payload — and it does, documenting background fields (backgroundType enum values, overlay, blur), separator shape structure with type/color/height/width/flip, and the clipPath/filter/opacity/shape treatment family. It falls short of 5 because the list ends in 'etc.' and the merge semantics for nested/array values are left to the schema's one-line note.

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?

Opening sentence states a precise verb+resource ('Update section-level styles') and enumerates the concrete properties (background, padding, gap, alignItems, justifyContent, textAlign, maxWidth). The scope word 'section-level' plus the separator/background sub-topics make it clear this is not the block, page, or settings updater. An agent can distinguish it from update_site_block/update_site_page/update_site_settings without opening a schema.

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?

Unusually rich: it gives explicit when-to-use (two adjacent sections with clearly different backgrounds), when-not to use ('Do not add them unless the user asked for them or the design clearly calls for one'), an alternative preference ('Prefer a bottom separator on the section above over a top separator on the one below'), and a prerequisite ('read them with get_site_section first'). The only blemish is that the named prerequisite tool doesn't match a sibling exactly (read_site_sections), and there is no guidance on choosing this over update_site_block.

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