Explore variations of an existing reference

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

The description discloses a critical side effect upfront: 'SPENDS IMAGE CREDITS.' It also explains that it creates a new child job and that the object identity is held fixed, which goes beyond the annotations (readOnlyHint=false, openWorldHint=true). While it doesn't mention every possible side effect, this is substantial behavioral context not present in the schema.

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 a single, well-structured sentence that front-loads the cost warning. Every clause adds value: the credit warning, the axis constraint, the identity requirement, and the child-job relationship. There is zero fluff or repetition.

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 tool with 8 parameters and no output schema, the description covers the core function and key side effects (credits, child job creation). It doesn't explain the return format, but it mentions creating a child job, which hints at a job reference. The waitSeconds behavior is defined in the schema, so the description doesn't need to repeat it. The remaining gaps (output details) are minor given the tool's role.

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?

The schema already covers 75% of parameters with descriptions (axis, seed, modelId, numImages, assetJobId, waitSeconds). The description adds nuance by stating that only ONE axis is varied and that the object identity is fixed, which clarifies the axis and assetJobId parameters. However, this is supplementary rather than essential, and width/height lack descriptions both in schema and description without compensation.

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 states a specific verb ('Generates variations') and a specific resource ('existing asset job'), and clearly scopes the action to 'ONE named axis' with a concrete list. It distinguishes itself from siblings by emphasizing it creates a new child job linked to the parent rather than starting from scratch. This leaves no ambiguity about what the tool does.

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 gives clear context for use: you have an existing asset job and want variations along a single axis. It implies alternatives by mentioning 'existing asset job' (vs. creating from scratch) but does not explicitly name sibling tools or state when not to use it. The instruction to hold object identity fixed further constrains when it is appropriate.

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