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

No annotations are provided, so the description carries the full burden. It mentions that values are discarded, but it does not disclose which parameter is used, what output is returned, whether network or disk access occurs for certain parameters, or how errors are handled.

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 extremely concise and front-loaded, consisting of one clear sentence with no fluff. However, the brevity comes at the cost of specifying which parameter is relevant, though that issue is more about completeness than conciseness.

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 has nine optional parameters and no output schema, the description is far too thin to be usable. It does not explain the relationship between the parameters and the JSON object, the expected output format, or the behavior when multiple parameters are provided.

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 every parameter has a schema description, those descriptions are misleading relative to the tool purpose. The 'json' parameter says 'validate', not 'count keys', and many other parameters (ref, url, city, feed, host, path, zone, query) appear unrelated to counting keys in a JSON object. No parameter is clearly designated as the JSON input.

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 'Count keys in a JSON object' at a high level, but it does not identify which of the nine parameters contains the JSON object. The 'json' parameter is described as 'JSON text to validate', which conflicts with the tool's stated purpose of counting keys, making the actual usage unclear.

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?

There is no guidance on when to use this tool versus alternatives like 'validate-json' or other sibling tools. The description and schema provide no selection criteria, prerequisites, or examples of appropriate use.

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