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

Annotations are not provided, so the description must carry the behavioral burden. It does disclose that values are discarded, but it does not explain whether keys are counted at the top level or recursively, what happens with invalid JSON, or what return format is produced.

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 short, front-loaded, and free of filler: the first sentence names the operation and the second adds the value-discarding behavior. It is well structured but too terse to compensate for the mismatched schema.

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?

With multiple schema parameters, no required fields, no annotations, and no output schema, a two-sentence description that never identifies the JSON input or the result format is severely incomplete. An agent cannot confidently invoke this tool based on the provided definition.

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?

Although schema coverage is 100%, the parameter descriptions are mismatched with the tool: ref, url, city, feed, host, json, and path are each described as being checked or discarded, and none is identified as the JSON object whose keys are counted. The description adds no mapping between the JSON object and any parameter.

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 operation — count keys in a JSON object — and explicitly notes that values are discarded, which gives it a clear core purpose. However, it does not connect that operation to any of the listed parameters, so an agent cannot tell which input represents the JSON object.

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 about when to use this tool versus its siblings. There is no mention of alternatives, exclusions, or context that would help an agent route to this tool rather than validate-json or domain-shape.

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