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

Given annotations already flag destructiveHint=true and idempotentHint=true, the description adds the crucial nuance the annotations cannot: partial-update semantics ('Only what is given changes'), per-style merge for typography, and whole-palette replacement for brandColors. That distinguishes merge from overwrite, which is the real risk here. It stops short of stating any permission/auth requirement or confirming that palette replacement is irreversible.

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 resource being changed, then merge semantics, then sibling routing — a sensible order with no filler sentences. It is somewhat dense in one block, and the parenthetical listing of typography attributes (font family, px, weight, line height, colour, case) duplicates schema detail that the agent will read anyway.

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 two-parameter nested mutation tool with 100% schema coverage, full annotations, and an output schema, nothing needed to call it correctly is missing: scope, merge-vs-replace behavior, read-back source, and sibling boundaries are all covered.

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 100% and the schema already carries the heavy lifting — including the per-style merge note and the 'replaces the current one' note for brandColors, plus priceFormat examples. The description's enumeration of typography properties and presets largely restates that, so it adds only marginal parameter meaning beyond the structured 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?

The description states a specific resource ('the catalog's own settings') and enumerates the exact surfaces it covers — title, page size presets/custom dimensions, priceFormat, brand palette, and typography for body plus h1–h4. It explicitly separates itself from edit_catalog (page content) and set_publish_options (publishing), so an agent can pick the right tool from siblings without opening schemas.

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?

It names two sibling alternatives verbatim and the boundary condition that selects each ('Page content is edit_catalog; publishing is set_publish_options'). It also routes the agent to get_catalog to read current values under `design`, giving the read-modify-write pattern explicitly.

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