add_text_overlay

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

With no annotations provided, the description carries the burden of behavioral disclosure. It explains that the tool writes to an output path, implying it is not destructive to the original video, and it describes the structure of text_elements. However, it does not mention potential side effects, error handling, or system requirements. This is adequate but not deeply transparent.

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-structured as a concise docstring with Args and Returns sections. It is front-loaded with the main purpose, then provides necessary details for each parameter without unnecessary verbosity. Every line adds value, making it efficiently sized.

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 complete for a tool of this complexity: it covers all parameters, provides detailed structure for text_elements, and states the return type. It lacks explicit information about failure modes or performance but is sufficient for an agent to invoke the tool correctly. Given the rich parameter documentation, a 4 is appropriate.

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?

The schema provides almost no parameter details (0% coverage), but the description compensates excellently. It enumerates required and optional keys for text_elements, including default values for font_size, font_color, positions, and box options. It also clarifies the purpose of video_path and output_video_path. This far exceeds the schema's minimal 'array of objects' definition.

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 tool's function: 'Adds one or more text overlays to a video at specified times and positions.' This is a specific verb+resource with clear scope, and it distinguishes itself from siblings like add_subtitles and add_image_overlay by focusing on text overlays with position/timing control.

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 provides clear context for use ('Adds one or more text overlays to a video at specified times and positions'), making it obvious when this tool is appropriate. It does not explicitly mention alternatives or exclusions, but the unique focus on text overlays at specific times/positions implies its distinct use case, earning a 4 rather than a 5.

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