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

The annotations provide no useful behavioral signals beyond non-read-only/non-destructive flags, so the description carries the burden. It adds meaningful context: the operation costs 20 credits and has a required ordering of API calls. However, it does not disclose whether the operation is synchronous or asynchronous, what the response contains, or other side effects.

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 description is compact and front-loaded with the main purpose and credit cost, followed by mode definitions and prerequisites. It avoids fluff but is somewhat dense; the mode mapping could be clearer, but overall every sentence contributes useful information.

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 10-parameter tool with no output schema, the description plus exhaustive schema descriptions cover the inputs and ordering well. However, it is missing return-value behavior, async status expectations, and a direct distinction from generate_ad_video, which an agent would benefit from when invoking and interpreting 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 description coverage is 100%, so parameter semantics are already well-documented. The description adds extra value by summarizing the mode-related scenarios, linking templateId and upload prerequisites to the process, and clarifying that service mode requires a prompt and creator while product mode needs both photo and creator.

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 clearly states the core action: 'turns a product photo into a finished ad', and defines the three modes (graphic/product/service). It does not explicitly distinguish itself from the sibling fattly_generate_ad_video, but the title annotation and the focus on 'ad' generation make the purpose reasonably clear.

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?

The description gives practical prerequisites: choose templateId with fattly_list_ad_presets and upload the product photo with fattly_upload_image first. It also explains which mode to use for different content types. It does not explicitly discuss when not to use this tool versus siblings like fattly_generate_ad_video, so it stops short of a 5.

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