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

Annotations already declare non-read-only, non-destructive, open-world and non-idempotent behavior, so the safety bar is partly carried. The description earns credit for disclosing what is preserved (widgets and content) versus what changes (colours, fonts, tile style), but it says nothing about reversibility despite an undo_change sibling, nor about whether re-applying the same theme is a no-op despite idempotentHint=false.

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?

Two tight sentences with the action and its effect front-loaded; nothing is redundant or padded. Slightly clipped to the point that the preservation clause could specify whether page-level overrides are kept.

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 mutation with full schema coverage and annotations, the definition covers inputs, effect scope, and defaults adequately. It omits any note about the return value or how to revert, which are minor given annotations and the undo_change sibling.

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 description coverage is 100%, so the schema already documents both the page default and the theme source; baseline 3 applies. The description reinforces the theme's provenance and the page default but adds no syntax, format, or constraint details beyond the schema.

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 ("Apply a theme ... to a page") and names the sibling tool that supplies the value (list_themes). The second sentence scopes the effect precisely, so an agent can distinguish this from sibling mutations like update_profile or set_language 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?

Clear workflow context: the theme id must come from list_themes and the page value from list_pages, with "home" as the documented default. It stops short of explicit when-not guidance (e.g., use set_language for locale changes, or undo_change to revert), so it's strong but not fully routing.

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