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

Annotations declare readOnlyHint=true, indicating a read-only operation, and the description does not contradict this. The description adds context about the tool's limitations (tiny subset, no $ref) and payment requirement, but does not clarify what the tool actually outputs or whether errors are returned for invalid data.

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, concise and front-loaded with the action and payment. It conveys key information, though the payment address inclusion may be seen as unnecessary detail, but it does not harm conciseness much.

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 tool's moderate complexity, the description covers purpose, key constraint (subset, no $ref), and payment requirement. No output schema is needed as the tool is likely to return validation results, but the description is brief; still, it is sufficient for basic usage.

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 parameters are documented with descriptions like 'JSON instance object or JSON text' and 'JSON Schema object or JSON text'. However, the description does not add further semantic detail beyond what the schema provides, so baseline 3 is appropriate.

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?

Purpose is clear: validate JSON data against a JSON Schema, specifying it's a tiny built-in subset with no $ref, and mentioning it is paid on Base. This distinguishes it from sibling tools like 'check' and 'domain', which are not about JSON validation.

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 for validating JSON data, but does not explicitly state when to use this tool versus alternatives, nor when not to use it. It mentions the paid nature and payment address, which is a contextual usage hint, but lacks direct guidance on choice among siblings.

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