Generate an image

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

Beyond the annotations (readOnlyHint=false, openWorldHint=true), the description discloses real cost behavior ('uses one image generation from the workspace's monthly plan allowance'), the dual return shape (image URL or job id), and that local reference files are uploaded on the caller's behalf. These are exactly the operational facts an agent cannot infer from the schema. It stops short of permissions/failure behavior.

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 sentences, front-loaded with purpose, then cost/return behavior, then the reference-parameter guidance. Every sentence carries distinct information with no filler.

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 10-parameter, no-output-schema generation tool, the description covers the essentials: what it produces, what it costs, both possible return shapes, and how references work. The job-id fallback path is adequately signposted; only the async polling details are left implicit.

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 coverage is 80%, so the baseline is 3, and the description adds genuine meaning on top: it groups the three reference_* parameters by intent (edit or restyle) and notes that local paths are uploaded automatically, clarifying path vs URL vs job-id choice. It adds little for seed/quality/resolution, which the schema already documents.

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 an ad image') plus the backing models (Grok, Luma), which cleanly separates it from adsoptimiser_generate_video, adsoptimiser_batch_generate and adsoptimiser_run_pipeline. The scope is unambiguous without opening any 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?

Explains the edit/restyle case for the three reference_* parameters and routes to adsoptimiser_get_job when generation is slow. It does not contrast against sibling generators (generate_video, batch_generate) or state when to prefer batch over single, so alternatives are only partially covered.

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