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

Annotations already declare it is not read-only, is open-world and not idempotent, so the safety profile is covered. The description adds genuinely useful context beyond that: it names the exact return value (drag offset as a percentage of background width) and discloses the cost model ('one credit per successful solve'), which is important for an agent deciding whether to retry. It does not say whether failed solves still consume credits or what errors look like.

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?

Two tight sentences with zero filler: purpose first, then the concrete output contract and the cost. Nothing is repeated from the title or schema.

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?

The tool is simple (3 params, 1 required), an output schema exists so return values need not be spelled out here, and the description covers purpose plus the credit cost. It stops short of describing failure/retry behavior or auth requirements, which is the only real gap for a paid, non-idempotent external call.

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%, so the schema already explains all three parameters, including the ordering of the one-vs-two image inputs and the 5-90 second timeout range. The description adds no parameter-level detail beyond what the schema provides, so the baseline of 3 applies.

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 (solves) plus the exact resource (GeeTest slider puzzle) and even specifies the return semantic (drag distance as a percentage of background width). The puzzle-type specificity distinguishes it from siblings solve_recaptcha_grid, solve_funcaptcha and solve_text_captcha without needing to name them.

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?

Usage is only implied by the name and by the sibling family of captcha solvers; the description never states when to pick this over the other solve_* tools or what preconditions exist (e.g. valid challenge images, account credits available). The credit statement hints at a billing context but is not framed as a prerequisite.

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