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

With no annotations, the description carries the transparency burden. It discloses the critical paid, two-step payment behavior ('call without x_payment to receive this call's exact terms... then call again with x_payment') and notes that the `pricing` tool is free. It does not mention output format or failure modes, but the main cost behavior is transparent.

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 three sentences, front-loaded with the primary purpose, followed by the payment workflow and a pointer to the pricing tool. Every sentence adds essential context, and there is no redundant repetition of schema details.

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?

This is a complex tool with a dual OCR/vision behavior and a payment mechanism. The description explains both behaviors and the full payment workflow, and it points to the pricing tool for exact costs. However, it does not explicitly state the return format (e.g., plain text string) or error handling, leaving a minor gap.

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?

The input schema already provides 100% parameter coverage with detailed descriptions (e.g., x_payment explains the exact two-step flow). The tool description adds little beyond what the schema states, mostly rehashing the x_payment behavior. Baseline 3 is appropriate given the high schema coverage.

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 the tool's function with specific verbs: 'Transcribe an image to text (OCR) or describe it via a vision model'. It also indicates steerability with a custom prompt, and this function is unique among the siblings (no other OCR/image description tool).

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 provides explicit guidance on the payment workflow: call without x_payment to receive terms, then call again with x_payment to settle. It also directs users to the free `pricing` tool for price lists, offering a clear alternative for pricing inquiries. It does not explicitly state when not to use this tool, but the context is clear.

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