Add an image/logo or text overlay to the timeline

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

With no annotations, description explains position coordinate system, dual modes, and read-only restriction. But it doesn't mention side effects like conflict resolution or default behaviors.

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 sentences with key information front-loaded. Each sentence adds value without redundancy.

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?

Covers core usage but lacks return value description, error handling, and default values for some parameters (e.g., opacity, size). Given 12 parameters and no output schema, more detail would help.

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?

Adds context beyond schema by grouping parameters into image/text modes and clarifying position interpretation. Schema coverage is 75%, so description complements well.

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?

Clearly states 'Overlay an EXISTING image/logo OR a text caption on the timeline at a specific point', distinguishing between image and text overlays. This differentiates it from siblings like add_image_from_file.

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?

Specifies modes for image vs text and mentions blocked in read-only mode. However, it doesn't explicitly guide when to use this vs alternatives like add_timeline_audio.

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