fablecut_frame

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

With no annotations, the description carries the entire burden and does so: it discloses the vision-capability requirement, that `path` is read in place and never copied, that ffmpeg must be on PATH, and that timeline mode runs in the open editor tab or falls back to a headless browser. These are non-obvious operational constraints an agent would otherwise discover only by failure.

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 critical fact (image output, vision requirement) is front-loaded before the modal breakdown, and the three modes are cleanly numbered. It is long for a single paragraph and the trailing ffmpeg/browser note is slightly buried, but nearly every clause carries distinct information.

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?

An 11-parameter tool with no output schema and no annotations is covered well: mode disambiguation, defaults, ranges, dependencies on a vision model and ffmpeg, and the fallback sibling are all addressed. Since the tool returns an image rather than structured data, no output-schema explanation is needed.

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 adds genuine meaning beyond the schema by explaining the mode-selection logic: `path` present means source frame, `frames` present means contact sheet, neither means timeline via `time`. It also clarifies the default image widths and the 2–60 frame range, though per-parameter detail largely duplicates the schema.

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?

"LOOK at the footage — returns an actual image, not just numbers" names a specific verb and output, and the three modes are enumerated explicitly (single frame, contact sheet, composed timeline). It differentiates itself from fablecut_analyze_reference by calling out that sibling as the non-vision fallback, so an agent can choose between them 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?

It states exactly when to use it ("before choosing a clip's `in` point, or to pick footage matching a blueprint's shots[] energy") and gives explicit alternatives and exclusions: pass `text:true` if not vision-capable, or skip this tool and use fablecut_analyze_reference. That is when/when-not/alternative coverage in full.

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