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

Annotations already indicate readOnly=false, destructive=false, and idempotent=false. The description adds that the challenge is 'live' but does not disclose additional behavioral traits such as expiration, rate limits, or authentication requirements. It doesn't contradict annotations but provides only modest extra context.

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 sentences with no filler. The main action is front-loaded, and the use case is provided in a second short sentence. Efficient and scannable.

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, with two fully documented parameters and annotations covering the safety profile. However, there is no output schema, and the description does not mention what the response looks like or any error conditions. This leaves a notable gap for the agent.

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 baseline is 3. The description mentions 'site key and allowed hostname,' reinforcing the two parameters, but adds no new semantic detail 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?

Clearly states the specific action and target: 'Create a live captcha.cc challenge for a site key and allowed hostname.' Distinguishes from siblings: make_siteverify_request verifies solutions and make_widget_snippet generates widget code, while this tool creates a challenge.

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?

Provides explicit use case: 'Useful for smoke tests and integration checks.' This gives clear context for when to use the tool, though it doesn't explicitly exclude alternatives or mention sibling tools.

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