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

Adds substantial context beyond the destructiveHint/idempotentHint annotations: edits land in the draft, partial input is merged, contrast is auto-repaired and reported via text_recoloured, the check costs ~20s, and a preview URL is returned. It also warns to tell the owner what changed, which is the kind of consequence info annotations can't convey.

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 core action, then side effects, then latency and return value. Dense and largely waste-free, though the contrast-repair explanation is repeated across the opening and the second sentence.

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 non-idempotent, destructive, multi-purpose mutation with no output schema, the description covers the side effects, the auto-repair behavior, the runtime cost, and the return value. Nothing an agent needs before invoking it 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?

Schema coverage is already 88%, so baseline is 3. The description still adds value by explaining the merge semantics of the colours object ('any subset; what you leave out is kept') and the relationship between preset_name and save_as, which is spread across separate schema fields.

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?

Opens with a specific verb and scope ('Change the site's colours and fonts in the draft') and immediately names the additional operations it bundles (brand name/tagline, preset re-apply, save_as). It also distinguishes itself from node-level siblings by telling the agent to prefer section/button data for single-element tweaks.

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 boundary case: 'For one section's surface or one button, prefer that node's own data over the theme.' That is a real alternative-selection rule. However, the brand name/tagline handling overlaps update_site_brief without saying which to prefer, and no explicit 'when not to use' for the whole tool.

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