Solve an image captcha

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

With annotations already indicating readOnlyHint=false and destructiveHint=false, the description adds useful behavioral context: it returns recognized text and notes that proxies are unsupported. This goes beyond the structured annotations without contradicting them, providing operational expectations for the agent.

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 sentences, front-loaded with the primary action and immediate use case. The second sentence provides a necessary limitation (proxy support) without any filler or redundancy. Every word contributes to understanding the tool's function and constraints.

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 simple parameter set (2 params, 1 required), full schema coverage, presence of an output schema, and annotations, the description covers the essential behavior, return value, and a key limitation. It could explicitly contrast with sibling captcha-solving tools, but the tool name and sibling list sufficiently fill that gap, making the description complete for the tool's scope.

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 covers 100% of parameters with detailed descriptions for 'image' and 'timeout'. The description only reiterates that the image is a captcha, which is already evident from the schema. With full schema coverage, the baseline of 3 is appropriate; the description adds no significant semantic value beyond the schema.

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 action: 'Read the text out of a distorted-text captcha image' with a specific resource and outcome. It distinguishes this tool from siblings by explicitly focusing on 'image captcha' versus Turnstile, reCAPTCHA, and Geetest, making the purpose unambiguous.

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 implies when to use it: when a distorted-text image captcha needs solving, and explains the result should be typed into the page's captcha field. It also provides a clear exclusion: 'Proxies are not supported for image captchas.' It does not explicitly name alternatives, but the sibling tool names and the 'image captcha' qualifier offer sufficient differentiation.

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