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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds valuable behavioral context beyond annotations: server-side validation of preset ids and the mode-matching constraint, which affect how the agent should use the results.

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 sentences with no filler. The primary purpose is front-loaded, and the critical ordering/validation note is delivered immediately after, making the description easy to scan and act on.

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 simple, read-only list tool with one optional parameter, the description covers purpose, resources returned (presets, scenes, avatars), and the essential prerequisite relationship with fattly_generate_ad. Annotations and schema cover safety and parameter semantics, so nothing necessary for 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 100%, and the mode parameter has a detailed enum description with concrete meanings for graphic, product, and service. The tool description does not need to repeat this; it only reinforces that presets work in matching modes, which is consistent with 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?

The description uses a specific verb ('Lists') with a clear resource scope: Ad Studio ad presets (templateId), scenes, and creator avatars. It also distinguishes itself from the generation sibling by explicitly naming fattly_generate_ad, so an agent can immediately tell this is the discovery/list tool.

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 explicit workflow guidance: 'Call this BEFORE fattly_generate_ad'. It also explains why ordering matters by noting preset ids are validated server-side and presets only work in their matching mode, which tells the agent when this tool is a prerequisite.

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