generate_image

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

With no annotations, the description must carry the full burden, and it does disclose three real behavioral facts: runtime, usage-limit consumption, and that existing files are preserved unless overwrite=true. It says nothing about failure modes, timeout behavior, or what a successful call returns or writes.

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?

Four tight lines, front-loaded with the core action and cost, then the parameters that most affect correctness. No filler 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?

A 10-parameter, annotation-free, mutation-style tool with no output schema needs far more coverage than this. Five parameters receive no explanation anywhere, which is a significant gap for an agent trying to invoke it correctly.

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% across 10 parameters, so the description must compensate. It only explains output_path, reference_images, reasoning_effort and the overwrite flag, leaving trim, max_size, tolerance, chroma_key and timeout_seconds entirely undefined for the agent.

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 gives a specific verb and resource ('Generate one image with Codex's built-in image tool') and the singular 'one image' subtly separates it from the sibling generate_images. It does not explicitly contrast with edit_image, so it falls short of a 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?

It supplies useful context about cost and latency ('counts against the plan's Codex usage limits', '~30-60 s') that helps an agent decide whether to commit to a call. However, it never states when to prefer this over generate_images or edit_image, nor mentions prerequisites such as login_status.

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