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

With no annotations, the description must disclose behavior. It only mentions that 'The body is discarded,' but does not explain what the tool returns (e.g., boolean, error message) or how it handles non-JSON inputs. The schema notes that many parameters are 'discarded after the call,' but the description lacks any detail on side effects or output format.

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 very concise: two sentences with no filler. The core purpose is front-loaded. However, the brevity borders on under-specification, omitting essential behavioral and usage details. It is efficient but not comprehensive, so it earns a 4 rather than a 5.

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 tool with nine parameters, no required fields, no output schema, and no annotations, the description is far too minimal. It fails to explain the overall behavior, return value, or how to combine parameters. An agent would be uncertain about what inputs are expected and what the tool does beyond a vague JSON check.

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 coverage is 100%, so each parameter has a description. The tool description, however, does not reference any parameters or add meaning beyond the schema. It does not explain how the parameters relate to the validation, nor does it compensate for the schema's cryptic references like 'discarded after the shape check.' The baseline of 3 applies since the schema is self-documenting, but the description adds no extra value.

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 clear purpose: 'Check whether a body is valid JSON.' This is a specific verb and resource. However, the input schema includes nine parameters for URLs, cities, feeds, hosts, paths, zones, and queries, suggesting the tool may validate more than JSON. The description does not clarify whether it handles only JSON or also other shapes, nor does it distinguish itself from sibling validators like file-path-ok or domain-shape.

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?

No guidance is provided on when to use this tool versus alternatives. The description says nothing about selection criteria, such as 'use this for JSON validation, use file-path-ok for file paths.' Given the many sibling validators, this is a significant omission.

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