Show Thumbnail Customizations

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

Annotations already declare readOnlyHint/openWorldHint/idempotentHint/destructiveHint=false, so the safety profile is covered. The description adds real behavioral value beyond that: it spells out the exact token scopes required, explains the all:delegate_to_contact_permissions delegation semantics, and clarifies that only explicitly-set customizations are returned.

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?

The useful content is front-loaded in the first sentence, and the permission requirements follow in a scannable block. The auth section is somewhat boilerplate-heavy (including the trailing fragment 'Read-only account operation'), but the information earns its place for an auth-gated read.

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 tool with a complete input schema and annotations covering the safety profile, the description supplies the missing pieces: what fields are returned, and the auth/delegation model. Without an output schema, the field enumeration is particularly helpful; only the empty/absent-customization response behavior is left unexplained.

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%, with both params (account, media_id) fully documented in the schema, so the baseline is 3. The description only indirectly reinforces 'for the video' (media_id) and says nothing additional about the account selector.

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 names a specific verb ('fetches') and resource ('thumbnail customizations') and even enumerates what the payload contains (still image URL, alt text, fit strategy, looping video thumbnail/text-overlay plugins), which cleanly separates it from the many sibling get_*_customizations tools. It stops short of explicitly naming its write counterpart update_thumbnail_customizations as the mutation path, so it is clear but not fully sibling-differentiated.

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?

Usage is implied rather than directed: 'explicitly-set' hints that unset/default customization values are not returned, and the permission block states prerequisites for calling it. However, it never says when to prefer this over get_media, get_customizations, or update_thumbnail_customizations, and gives no when-not guidance.

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