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

With no annotations, the description carries the full burden, and it does disclose one meaningful behavioral trait: the layer 'Compiles and test-renders it before saving,' telling the agent there is validation with a possible failure path before persistence. That is genuinely useful. It still omits auth/permission requirements, what happens on compile or render failure, whether the item can be edited afterward, and any latency expectations.

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?

Three short sentences, front-loaded with the action, followed by behavioral disclosure and the prerequisite. Zero filler; every sentence earns its place.

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?

This is a complex, 20-parameter tool with nested objects and no output schema, so the description needs to carry more weight than a simple CRUD tool. It covers purpose, key behavior, and a prerequisite, but leaves gaps around failure semantics of the compile/test-render step, whether the created overlay is addressable by a returned id (relevant given the sibling update_overlay_item / delete_overlay_item tools), and timeline placement requirements.

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 80% across 20 parameters, so the schema already documents nearly everything (size, position, enter/exit, keyframes, legacy shorthands, remotionConfig.source). The description adds no parameter-level meaning, which is acceptable given the high coverage — baseline 3 is correct here.

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 and resource: 'Create a custom Remotion React animation layer on the edit timeline.' This is enough to distinguish it from the sibling add_text_overlay and add_media_overlay tools, since it is explicitly a Remotion React layer rather than a preset overlay. It stops short of differentiating further (e.g. vs. update_overlay_item or add_overlay_track), but the resource identity is 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?

'Call get_remotion_layer_guide first' gives an explicit prerequisite, which is real routing guidance. However, it says nothing about when to choose this tool over the other overlay-creation siblings, nor what conditions make a Remotion layer the right choice. Usage is implied (custom React animation) but not contrasted against alternatives.

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