Generate image

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

Annotations already declare readOnlyHint=false, destructiveHint=true, and idempotent=false, so the safety profile is covered. The description adds one genuinely useful behavioral fact not in the structured fields — the return value is an image URL — but says nothing about credit spend, per-model limits, or the long-job polling path, so it adds only modest context beyond the annotations.

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?

Three short sentences, front-loaded with the core capability, then the editing path, then the return value, then the sibling exclusion. No filler or redundancy.

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?

With no output schema, stating 'Returns the image URL' closes the most important gap for a 12-parameter generative tool. The remaining complexity (cost confirmation, callbacks, provider_options) is fully handled by the schema, so the description is complete enough for correct invocation, though it could note the cost/credit dimension.

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 the schema already documents all 12 parameters thoroughly, including defaults, wait/callback semantics, and the provider_options escape hatch. The description only restates the image_urls editing usage and the default model, adding little beyond what the schema provides; 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?

States a specific verb and resource ('Generate or edit an image') and covers both modes (generation and editing) in one clause. It explicitly distinguishes itself from the sibling upscale_media, so an agent can route between the two without opening either schema.

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?

Gives concrete usage conditions: pass image_urls to edit or supply reference images, and defer to upscale_media for upscaling. What's missing is guidance on when to prefer this over generate_video/edit_video or how the wait/callback flags change the calling pattern — but those are surfaced in the schema rather than the description.

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