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

With no annotations, the description carries the full burden of behavioral disclosure. It does state that 'The body is discarded,' which is a useful side-effect note. However, it doesn't disclose what happens on invalid JSON (e.g., return value, error behavior), whether the tool performs any network or disk access (though some schema descriptions hint at 'no disk access'), or how the many other parameters relate to the tool's behavior. The description is too sparse to convey the tool's full behavioral profile.

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 with no wasted words, which is concise. However, it is under-specified for a tool with nine parameters and no output schema. It lacks structure (e.g., no separation of purpose, usage, and behavior) and omits critical information. It is not a well-structured description, but it is not verbose either.

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 complexity (9 optional parameters, no output schema, no annotations), the description is far from complete. It doesn't explain what the tool does with the other parameters (e.g., ref, url, city), what the return format is, or how the JSON validation integrates with the other fields. The schema descriptions help but don't tie the tool together. An agent would struggle to know when and how to call this tool correctly based on the description alone.

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 each parameter is already documented in the schema. The tool description adds no parameter-level semantics beyond what the schema provides. The description mentions 'body' but doesn't map it to the 'json' parameter, and it doesn't explain the purpose of the other eight parameters. Since the schema does the heavy lifting, a baseline of 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?

The description states a specific action ('Check whether a body is valid JSON') and a clear resource (JSON body). It distinguishes from sibling tools that check other shapes (e.g., domain-shape, figma-url-shape) by focusing on JSON validation. However, it doesn't clarify that the JSON input is passed via the 'json' parameter, and the presence of many unrelated parameters in the schema creates ambiguity about the tool's actual scope.

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 no guidance on when to use this tool versus alternatives. It doesn't mention conditions, exclusions, or prerequisites. There is no indication of when to prefer validate-json over other validation tools like browser-url-ok or file-path-ok. The agent is left to infer usage from the name and description alone.

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