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

Annotations already establish read-only, idempotent, non-destructive behavior, so the burden is lighter; the description still adds real value by explaining that pixels:false costs no image and by defining the fingerprint metrics (nonBlankRatio near 0 = black/empty, colorRange near 0 = featureless). It does not discuss batching limits or failure modes beyond the 12-timestamp cap, which is in the schema.

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?

Front-loaded with purpose and output shape, then guidance, then interpretation hints. Every sentence carries actionable information; the only slight redundancy is restating the 12-timestamp cap already in the schema.

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?

There is no output schema, and the description fully compensates by describing the return value (single grid image with labelled cells plus per-cell fingerprint) and how to read it. For a read-only inspection tool with 100% schema coverage, nothing an agent needs to call it correctly is missing.

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, but the description goes beyond the schema by explaining how to interpret the fingerprint values produced under pixels:false and by pairing atSec with get_media's sceneSamples. It makes the cost/benefit tradeoff of the pixels flag concrete rather than just restating its type.

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?

States a specific verb and resource (inspect frames inside a source asset) and precisely describes the output: one contact-sheet grid plus a per-cell fingerprint. It also explicitly distinguishes itself from the sibling inspect_timeline ('Shows the RAW source; use inspect_timeline for the composed cut'), so an agent can route correctly without opening either schema.

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?

Gives explicit conditional guidance: start with pixels:false when only checking for emptiness, request pixels when judging subject/framing/legibility. It names the alternative (inspect_timeline) and a complementary tool (get_media sceneSamples for a storyboard), covering when-to-use, when-not-to-use, and what to combine with.

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