Add video fade

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

The description adds value beyond annotations by stating that the source is unchanged and output is created/overwritten. It aligns with destructiveHint and readOnlyHint, and provides context on file handling.

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, front-loaded with the core purpose, no wasted words. Every sentence contributes to understanding the tool's function and key parameters.

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 covers the main functionality and matches the tool's complexity. The output schema exists, so return values need not be explained. Minor omission: no mention of optional parameters like crf and preset, but these are in the schema.

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?

With 100% schema description coverage, the description reuses some parameter info but does not add new meaning beyond the schema. It provides a brief usage example for fade_in and fade_out, but the schema already covers them.

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 verb 'render' and the resource 'fade-in and/or fade-out effects onto an existing video'. It distinguishes the tool from siblings by specifying the exact effect and that the source file remains unmodified.

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 explicitly explains when to use fade_in vs fade_out and mentions output_path overwriting. It does not directly compare to alternatives, but the specific fade effect and sibling context make the usage clear.

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