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Set Upstream Key Sources

atem_set_usk_sources
Idempotent

Configure fill and cut sources for upstream keyers on ATEM video switchers to manage keying effects during live production.

Instructions

Set the fill and/or cut sources for an upstream keyer.

Args:

  • me (number, optional): Mix Effect bus (default: 0 for ME1)

  • usk (number): Upstream keyer number (0-based)

  • fillSource (number, optional): Input to use as fill

  • cutSource (number, optional): Input to use as key/cut

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
meNoMix Effect bus
uskYesUpstream keyer number (0-based)
fillSourceNoFill source input number
cutSourceNoKey/cut source input number
Behavior3/5

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

Annotations indicate this is a non-destructive, idempotent write operation (readOnlyHint=false, destructiveHint=false, idempotentHint=true). The description adds no behavioral context beyond this, such as rate limits, error conditions, or effects on other system states. With annotations covering core traits, the description meets a baseline but adds minimal extra value.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is front-loaded with the core purpose in one sentence, followed by a structured 'Args' list. It avoids redundancy but could be more concise by integrating parameter details into the main text or omitting the schema-repetitive 'Args' section, as it doesn't add unique value.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's moderate complexity (4 parameters, no output schema), annotations provide safety and idempotency info, but the description lacks usage context, error handling, or examples. It's minimally adequate but leaves gaps in operational guidance, especially for a write tool with no output schema to clarify results.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, with all parameters documented in the schema (e.g., 'me' as 'Mix Effect bus', 'usk' as 'Upstream keyer number'). The description's 'Args' section repeats this information without adding meaning, syntax examples, or constraints beyond the schema, so it meets the baseline for high schema coverage.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the verb ('Set') and resource ('fill and/or cut sources for an upstream keyer'), specifying the exact action and target. It distinguishes from siblings like 'atem_set_usk_on_air' (which controls on-air state) and 'atem_set_dsk_sources' (which targets downstream keyers), providing precise differentiation.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

No guidance is provided on when to use this tool versus alternatives. It doesn't mention prerequisites (e.g., needing an upstream keyer configured), exclusions, or comparisons to similar tools like 'atem_set_dsk_sources' for downstream keyers, leaving the agent without contextual usage cues.

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

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