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

Annotations already declare readOnlyHint and openWorldHint, so the description is not burdened with establishing safety. It adds useful context by mentioning the optional system prompt and per-call cost, but it does not disclose output format, failure behavior, or supported image constraints beyond 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 two short sentences: one states the tool's function and optional prompt, the other states the cost. It is front-loaded and contains no filler or redundant restatement.

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 only three parameters, annotations, and a clear schema, the core invocation is adequately covered. However, the absence of an output schema means the description should ideally indicate what the response looks like (e.g., text answer), and it does not help an agent choose between this and similar sibling tools.

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%, with image, prompt, and system_prompt each already explained. The description adds marginal value by noting the optional system prompt and reinforcing open-ended questions, but the schema carries most of the parameter meaning.

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 clearly states a specific action ('Ask any question about an image') and identifies the optional system prompt. It is unambiguous but does not distinguish itself from similar siblings like answer_picture_question, describe_image, or image_to_text.

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?

The description says 'any question' but provides no guidance on when to use this tool versus the many similar image-analysis siblings. There are no exclusions, alternatives, or selection criteria, so an agent must infer the appropriate context.

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