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

The annotation readOnlyHint=true already signals safety. The description adds valuable behavioral detail beyond annotations: it returns per-error JSON pointers and rules, and includes unexpected property names and valid enum values in messages. This helps the agent understand the tool's output without being contradicted by 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?

The description is three focused sentences. The first states the core action and output, the second adds useful output detail, and the third gives a direct usage instruction. Every sentence 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 description fully covers the tool's purpose, output shape, and usage context. While there is no output schema, the description explains exactly what the tool returns per error. Parameter details are already present in the high-coverage schema, so nothing critical is missing for an agent to call it correctly.

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 schema already documents all parameters thoroughly. The description does not add much parameter-level semantics beyond the schema, which makes the baseline 3 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?

The description states a specific verb ('Validates'), a clear resource ('behavior or resource pack JSON file against the official schema'), and the output format ('JSON pointer, violated rule, readable message'). It is unambiguous and distinguishes validate_json from sibling validators like validate_command, validate_python, and validate_script.

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 gives an explicit usage directive: 'Run every JSON file you produce through this before handing it to the user.' This is clear context for when to use the tool, though it does not explicitly discuss when not to use it or name alternatives.

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