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

Annotations already declare openWorldHint=true and destructiveHint=false, but the description adds materially new behavior: no credit consumption, vendor billing on the account's key, and that the call returns a generation object that must be fetched with get_generation. It does not mention latency, async polling, or failure modes, which keeps it from a 5.

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?

Two sentences, densely packed but front-loaded with the core action, then parameter mechanics, then cost and result handling. No filler or restatement of the title.

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 complex tool with nested objects and three required parameters, the description covers the full invocation path plus cost and retrieval, and an output schema exists so return-value detail is unnecessary. Minor gaps remain around synchronous vs. asynchronous execution and error behavior for an open-world call.

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?

With 0% schema description coverage across six parameters including a nested media object, the description carries the whole load: it maps endpoint+slot to the concept of a 'mode' sourced from list_own_models, explains media values as { generation_id } or { upload_id } references, and explains that 'inputs' are passed by field name. This adds meaning well beyond the bare schema types.

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 and resource ('Run one of the account's own models on its own key') plus a concrete scope qualifier that separates it from the built-in generation tools (generate_image, generate_with_recipe) in the sibling list. An agent can identify what this does and why it differs without opening the 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?

It gives clear operating context: models come from list_own_models, the mode is endpoint+slot, and results are read via get_generation, which effectively chains the workflow. It never explicitly says when NOT to use it (e.g., use generate_image for platform-hosted models), so it stops short of full routing guidance.

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