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

Annotations already declare readOnlyHint and idempotentHint. The description adds valuable behavioral context including 'Returns the specific violations, not just true/false' and clarifies the check is limited to 'required + types only', not full JSON Schema. This goes beyond the annotations.

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?

Every sentence in the description earns its place: what it does, what it returns, its limitations, and when to use it. The structure is front-loaded with the core purpose and remains tight without redundant details.

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 parameters and an output schema exists. The description covers purpose, usage, limitations, and return behavior comprehensively. There is no need to explain return values given the output schema, and the description sufficiently covers all relevant context.

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 already provides 100% coverage with descriptions for both parameters. The description reinforces meaning by explaining the 'schema' parameter checks 'required[] and properties[].type', which adds context beyond the schema text. Baseline is 3, and this extra context warrants a 4.

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 tool validates JSON text and optionally checks required keys and types. It uses specific verbs ('Checks', 'Returns') and distinguishes itself from siblings like json_format by focusing on validation rather than formatting.

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 provides a concrete use case: 'Use before feeding generated JSON into something that will fail on it.' It also excludes full JSON Schema validation, but does not explicitly name alternative tools. Still, the guidance is clear and actionable.

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