add_vignette

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

With no annotations, the description carries the full burden, and it does disclose the key behavioral trait: the effect is applied to a new layer on top, so it is non-destructive and reversible via opacity or deletion. That is genuinely useful beyond what structured fields provide. It does not say whether the tool needs an active selection, what the new layer is named, or what the result looks like on 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?

A single compact sentence with the core effect front-loaded and the lifecycle note trailing. Nothing is redundant or padded. It is arguably too terse for a four-parameter tool, but as prose it is well-formed.

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?

Four parameters with zero schema descriptions, no annotations, and no output schema mean the description is the only documentation — and it explains none of the inputs. For a tool with adjustable size, color, strength, and blend mode, the definition leaves the agent guessing at nearly every argument.

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 0% — the four parameters (size, color, strength, blend_mode) have only titles and defaults. The description compensates only obliquely: 'darken' and 'tint' imply color, 'edges' implies size, and 'darken' implies strength, but no parameter is named or explained. An agent cannot learn valid ranges, units, or what blend_mode values are legal from this definition.

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 pairs a specific verb ('Darken (or tint)') with a specific effect ('the edges') and states the mechanism ('on a new layer on top'). That is far clearer than the bare name 'add_vignette' and an agent can predict the visual result. It stops short of distinguishing itself from sibling effect tools like apply_filter or adjust_image, so it lands at 4 rather than 5.

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?

Usage is only implied: the phrase 'adjust its opacity or delete it later' signals a non-destructive workflow, which hints at when this is preferable to a baked-in filter. There is no explicit statement of when to choose add_vignette over apply_filter, nor any prerequisite such as an open document or active layer. The agent must infer the context.

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