create_custom_animation

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

With no annotations, the description carries the behavioral burden, and it delivers substantial detail: object types, individually animatable properties, expression functions, and render order ('Later objects appear on top of earlier objects'). It does not describe output file behavior or side effects, but the 'create' nature and output_name parameter make the main behavior clear.

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 well-organized with bullets, a code example, and a scannable list of use cases. A few phrases are redundant with the opening ('Multiple objects can exist in the same scene'), but the structure is front-loaded and every major section supports invocation.

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?

The description is strong for a simple circle-based animation but incomplete for the full claimed surface. It supports text objects yet gives no hint of text-specific fields, and it does not explain coordinate system, expression timing, or returned output. Given no output schema and no annotations, an agent would still need to guess for advanced object types.

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 compensate. It does add essential meaning for the 'objects' parameter via a concrete circle example and expression-language documentation, but top-level parameters like fps, duration, background, and output_name are not explained in the description. The defaults and names are somewhat self-explanatory, leaving this minimally viable.

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 opening line is specific: 'Create a complete multi-object animated video from scratch.' The description further identifies the tool as a 'general-purpose procedural animation engine' and lists supported object types and animation properties, which distinguishes it from specialized siblings like create_stick_figure_runner or create_pan_animation.

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 clear usage context: use this when you need a multi-object, procedurally driven animation built from primitives. It does not explicitly name sibling alternatives or state when not to use it, but the 'general-purpose' framing and complex scene examples imply the intended scope.

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