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

Annotations already cover read-only, open-world, non-idempotent, non-destructive. Description adds crucial behavioral details: it is a paid call ($0.01/call via USDC or card), failed calls are free, and repeats are not free due to charging. This directly informs cost and non-idempotency.

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?

Front-loaded with the core purpose, then adds file type limits, use cases, pricing, and behavioral notes in a tight, logical flow. Every sentence carries useful information.

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?

Given the rich annotations and no output schema, the description covers all needed aspects: purpose, supported formats, size limit, pricing model, and read-only behavior. An agent has everything necessary to decide and invoke 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 coverage is 100%, so the schema already fully documents both parameters. The description reinforces the URL's public nature and the question's purpose, but adds no format or syntax details beyond what the schema provides.

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: 'Vision model for an image at a public URL' with two clear modes (describe or question). It distinguishes itself from general text AI tools by focusing on image analysis and even lists concrete use cases like alt text and OCR.

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 clear contexts for use: alt text, OCR-style reading, chart reading, content checks. Does not explicitly state when not to use it or name a sibling alternative, but the image-specific focus makes its niche clear.

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