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

Beyond the annotations (readOnly, idempotent, non-destructive), the description discloses key behavior: auto-detection of direction ('It works out which one you gave it') and error handling ('A parse failure comes back with the parser message instead of silently producing something that looks fine and is not'). This adds valuable context beyond what the annotations provide.

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 concise (3 sentences) and front-loaded with the primary action. Each sentence adds distinct value: functionality, auto-detection/error behavior, and usage context. There is no fluff or repetition of schema 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?

For a simple conversion tool with an output schema present, the description is complete. It covers function, behavior on failure, and practical use cases. The annotations and output schema handle safety and return format, so the description doesn't need to repeat those details.

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 has 100% coverage with descriptions for both parameters ('to' and 'text'). The description adds context about auto-detection and that the direction parameter is optional, but it doesn't provide additional syntax or semantics beyond the schema. This meets the baseline for well-documented schemas.

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 exact function: 'Converts JSON to YAML or YAML to JSON.' It also highlights auto-detection of input format, distinguishing it from sibling tools like json_format (formatting) and validate_json (validation). The scope is specific and immediately understandable.

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 explicit use cases: 'Use when a config, a CI file, or a Kubernetes manifest needs to be in the other format.' This gives clear context for when to use the tool, but it doesn't mention alternatives or when not to use it, so it stops short of a 5.

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