Analyse brightness and colour

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

Annotations already establish readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds valuable non-obvious behavior beyond that: analysis is performed on sampled frames, and 'each sample is a separate fast seek,' implying quick, non-contiguous seeks rather than full decode. It also says 'Answers immediately,' setting synchronous performance expectations.

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 description is front-loaded with the core function and uses a short explanatory paragraph to convey use cases, followed by a concise behavioral note. It is slightly wordy ('This is how a grade gets checked rather than guessed at') but every sentence contributes purpose, usage, or behavior.

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?

The description covers purpose, use cases, sampling limitation, and speed, and the output schema exists for return details. However, the ambiguous start/end parameters and lack of input_path/project context are significant gaps for correct invocation, making it adequate but not complete.

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 only 25%; only 'count' is described ('Frames to sample'). The tool description does not compensate for start/end/input_path semantics — it doesn't define units for start/end, how samples are distributed across the range, or the meaning of input_path in relation to existing projects. 'Across sampled frames' only weakly hints at count/range behavior.

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 first sentence uses a specific verb and resource: 'Measure brightness and colourfulness across sampled frames.' It clearly differentiates from sibling tools by framing itself as an analysis/measurement tool (not color_grade/apply_curves) and lists concrete diagnostic use cases like shadow crush, clipping, and greyscale detection.

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?

The description gives clear context for when to use it: checking a grade rather than guessing — evaluating crushed shadows, clipped highlights, greyness, and exposure consistency across shots. It does not explicitly name alternative tools or exclusions, so it stops short of a 5.

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