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

Beyond the annotations (readOnlyHint=false, idempotentHint=false, destructiveHint=false), it discloses credit consumption, that an already-running job is joined and not charged again, that a long cutout returns a Job ID to poll with wait_for_jobs, that results can be checked with preview_frame, and that missing photo/footage is surfaced for the user to set rather than guessed. That is substantive behavioral context not available in structured fields.

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?

Purpose is front-loaded in the first sentence and every later sentence adds operational value (delegation, credits, job polling, verification). A few clauses are densely packed ('when one covers the seconds the effect plays over'), but there is no filler.

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?

For a mutation tool with no output schema, the description covers the trigger source, side effects, credit cost, async return shape, and verification path. It is close to complete; only the concrete cost magnitude and exact error conditions are left implicit.

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%, so both parameters are already documented, and the description only restates that clipId is the effect's clip id (from read_film's Effects waiting) without adding format or syntax detail. projectId is not addressed in the description at all, leaving the schema to carry it — baseline 3 applies.

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 and resource ('Make what an effect already in the film still needs, and link it in: its person mask or its face') and immediately scopes it against the alternatives cutout_person and track_faces. An agent can tell this is the orchestration/wiring tool rather than a raw mask or face generator.

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 the trigger context (effects listed under 'Effects waiting' by read_film), the decision rule for reusing an existing mask/face versus running cutout_person/track_faces, and that an in-flight run is joined rather than restarted. It stops short of an explicit 'do not use this when…' exclusion, so a 4 rather than 5.

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