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

The description discloses that the original is untouched, it returns a NEW video, is executed by ffmpeg in seconds for ~2 credits flat, and has no AI model. It also clarifies brand asset loading behavior. This adds substantial context beyond the annotations (readOnlyHint=false, etc.) without contradicting them.

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 long but information-dense; every sentence contributes. It is front-loaded with purpose and constraints. Could benefit from bullet-point formatting for the operation list, but it remains efficient and scannable.

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?

Given the tool's complexity and absence of an output schema, the description covers what it does, how (ffmpeg, no AI), constraints (6 ops, order), brand handling, and exclusions. It lacks error-handling details but is complete enough for correct invocation.

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 coverage is 100%, so the baseline is 3. The description adds operational semantics: 'Up to 6 ops per plan, applied in order', 'append end card ... ADDS its seconds', and 'brand assets ... load from the workspace brand automatically; override per-call'. This enriches parameter understanding beyond the schema alone.

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 states a precise verb ('MECHANICAL post-production') on a specific resource ('EXISTING rendered video (its served mp4 URL)'), and enumerates the exact operations it supports (trim, speed, mute, audio_gain, fade_out, append_card, watermark, grain). It explicitly distinguishes itself from generate_video/render_ad, making its scope unmistakable.

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?

It says 'The lane for: ...' listing specific use cases, and explicitly instructs 'NEVER use generate_video/render_ad for these mechanical asks.' This provides clear when-to-use and when-not-to-use guidance, even if it does not contrast with every sibling video tool, the primary alternatives are covered.

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