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

Annotations already declare readOnly/idempotent/openWorld, so the description's job is to add context, which it does by disclosing the return payload shape (metadata, caption, timestamped transcript, keyframes from scene cuts) and the platform-limitation behavior. It stops short of describing failure modes or cost/latency traits.

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 short paragraphs, front-loaded with what it does and what it returns. Every sentence carries information – the platform caveat and the return-value summary both earn their 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?

With no output schema, the description correctly steps in to describe the return payload, and the 100%-covered input schema handles the parameters. It's nearly complete; only error behavior beyond the 'not available yet' note is unspecified.

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 100% with per-parameter descriptions for layout, from_slide, max_frames, and include_transcript, so the schema carries the semantics. The description adds only indirect hints (keyframes sourced from scene cuts, photo posts/carousels implying from_slide), warranting the baseline 3.

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+resource ('Watch a short video') and enumerates exactly which platforms it covers, plus the non-video Instagram photo/carousel case. It does not differentiate from siblings reel_transcript or zoom_frames, so it falls short of a 5.

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 gives explicit inclusion and exclusion guidance ('YouTube and Threads links get a short "not available yet" note'), which tells the agent when this tool will and won't work. It never names the sibling alternatives, though, so the agent gets no routing guidance between watch_reel, reel_transcript, and zoom_frames.

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