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

With no annotations provided, the description carries the full burden of behavioral disclosure. It states 'Values discarded', which implies the tool only returns a count, but it does not explain what happens with non-JSON inputs, what the return value represents for other parameters, or how the tool handles multiple inputs. The description is too minimal to inform the agent of side effects, error conditions, or the nature of the operation beyond a vague key-count.

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 short sentences), which is structurally clean. However, it is under-specified for a tool with nine parameters and no annotations. Conciseness is not the issue; the lack of necessary content is. It earns a middle score because it is efficient but sacrifices completeness.

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 has nine optional parameters, no annotations, and no output schema. The description does not explain what the tool does with each parameter, what it returns (beyond a vague key count), how it handles multiple inputs, or any behavioral details. An agent would be unable to correctly invoke this tool for most of the parameters listed in the schema. The description is critically incomplete for the tool's apparent complexity.

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 has a description. The main description adds a bit of context (that it counts keys in a JSON object) but does not clarify how the other eight parameters relate to that goal. The parameter descriptions themselves are informative (e.g., 'Git ref name; discarded after the shape check'), but the tool description does not integrate them or explain the overall mechanism, so it adds limited value beyond the schema.

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 and resource (count keys in a JSON object), but it is misleading because the input schema accepts nine unrelated parameters (ref, url, city, feed, host, json, path, zone, query), many of which have nothing to do with JSON objects. The description fails to convey the tool's actual scope, which appears to be a generic shape checker based on the parameter descriptions (e.g., 'discarded after the shape check', 'discarded after the length check'). It does not distinguish from siblings like validate-json or search-query-len.

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 given on when to use this tool versus alternatives. The description does not mention any conditions, prerequisites, or scenarios where this tool should be preferred over siblings such as validate-json or search-query-len. The parameter descriptions hint at multiple use cases (URL, city, RSS, timezone, etc.), but the tool description never addresses how to choose among them.

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