captcha.cc Human Verification

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.

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

Annotations already declare readOnlyHint=true and idempotentHint=true. The description adds valuable context by clarifying it 'returns an example' rather than performing an actual request, and emphasizes 'exactly once' redemption. This goes beyond the structured annotations and helps the agent understand the tool's output nature.

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 a single sentence that is front-loaded with the action ('Return a server-side fetch example') and includes only essential detail ('redeeming a captcha.cc proof token exactly once'). Every word earns its place, with no redundancy.

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 and the description clearly conveys its purpose and output nature. However, the lack of parameter documentation is a notable gap. The presence of an output schema is not required, but without it, the description could still explain what the returned example looks like or provide parameter context, making it only minimally complete.

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 0% and the description does not explain the parameters (secret_env_var, proof_token_expression) or their roles. While the parameter names offer some hints, the description fails to compensate for the missing schema descriptions, leaving the agent without clear guidance on how to use the two parameters.

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 uses a specific verb ('Return') and identifies a clear resource (server-side fetch example for redeeming a captcha.cc proof token exactly once). It distinguishes itself from sibling tools (create_challenge, make_widget_snippet) by focusing on server-side verification code generation.

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?

No guidance is provided on when to use this tool versus alternatives. It doesn't mention scenarios like server-side verification needs or exclude client-side options, and sibling tools are not referenced. The usage context is implied from the purpose but not explicitly stated.

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

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds functional context by explaining that the snippet mounts the widget and submits the proof token, which is consistent with a read-only code generation tool. However, it does not disclose edge cases or limitations (e.g., snippet language or integration steps), though this is minor for a simple generator.

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 a single sentence that is concise and front-loaded with the primary action. Every word adds value, with no redundancy or filler. It is appropriately sized for the tool's simplicity.

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 nature of the tool and the absence of an output schema, the description adequately states what is returned (a snippet) and what it does. The 100% schema coverage for parameters means the description need not elaborate on parameter usage. It is complete for a code generation tool, though it could arguably mention prerequisites or output format, but those are not critical.

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%, with clear descriptions for site_key, form_id, element_id, and submit_path. The tool description itself provides no parameter-level details, but the schema fully covers meaning, 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?

The description uses a specific verb ('Return') and clearly identifies the resource ('minimal browser SDK snippet') and its function ('mounting captcha.cc and submitting the proof token'). This distinguishes it from siblings like create_challenge (server-side challenge creation) and make_siteverify_request (server-side verification).

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 usage—when you need a client-side snippet to mount the widget and submit proof tokens—but it does not explicitly state when NOT to use it or mention alternative sibling tools. There is no exclusion or direct comparison, so guidance is only implied.

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