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

Annotations already flag this as a non-read-only, destructive mutation, and the description corroborates by saying it repaints every slide in one call. It adds a genuinely useful preservation rule ('Font sizes are kept') and a verification tip (napkin_slide_view). However it never states explicitly that existing per-slide customizations beyond font size are overwritten.

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-loads the core action before the theme catalog, and the catalog is justified because the schema carries no enum. The parenthetical character notes ('Gets out of the way', 'Softer than it sounds') are slightly decorative, but each still helps a model pick a theme, so waste is minimal.

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 destructive, annotation-covered mutation with a fully documented schema and no output schema, the description supplies everything needed: scope of change, what is preserved, the full theme vocabulary, defaults, alternatives, and how to verify the result.

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%, so the baseline is 3, but the description adds real value the schema lacks: it enumerates the six built-in theme keys (the schema exposes no enum and only says 'a built-in theme key') and explains the brand/brand:<kit> distinction and the accent concept. That is meaningful 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?

States a specific verb and resource ('Paints every slide of a deck with a theme') and enumerates exactly what changes: slide background, heading/body typefaces, and text colors. It also distinguishes itself from siblings by pointing to napkin_draw for one-off shape edits, so an agent can tell it apart from the other napkin_* 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 an explicit default ('Prefer "brand" ... unless the user asks for something else'), names the alternative for a different job ('For one-off colors or sizes on a single shape, use napkin_draw's `updates` instead'), and points to napkin_slide_view to verify. When-to-use, when-not, and alternatives are all covered.

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