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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds real value beyond that: it explicitly states nothing is published and that the output is a preview URL openable in a browser, clarifying the side-effect-free, inspectable nature of the operation.

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 and the 'without publishing' qualifier, then the parameter guidance. The long ad_format enumeration is verbose but earns its place because the schema carries no enum, so it is necessary rather than padding.

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 read-only preview tool with annotations covering safety and an output schema covering the return structure, the description supplies the missing pieces: the non-publishing guarantee, the URL result, the creative_id provenance, and the placement enum. Nothing essential to correct invocation 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 description coverage is 0%, so the description must carry the burden, and it does: it documents the source of creative_id and enumerates all valid ad_format values, which the schema does not provide (no enum declared). Only the default and the required/optional distinction are left to 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+resource (renders a visual preview of an ad creative) and immediately distinguishes scope with 'WITHOUT publishing it', which separates it from the many create_/update_ siblings. An agent can tell what this does without opening the 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?

Provides clear usage context ('great for reviewing before launch') and tells the agent where creative_id comes from (create_meta_link_ad / create_meta_video_ad / create_meta_carousel_ad / get_ad_details). It lacks an explicit when-not or named alternative, but the workflow placement is unambiguous.

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