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

With no annotations, the description carries the full burden. It does disclose that values are discarded and several parameters mention being discarded after checks, but it does not explain side effects, failures, or whether anything is read, fetched, or stored.

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 brief and front-loaded, but it is so terse that it omits essential usage context. The sentence 'Values discarded' adds a small behavioral detail, but the overall structure does not compensate for the ambiguous parameter set.

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 9 optional parameters, no output schema, and no annotations, the description is far from complete. It does not say which parameter contains the JSON object, whether top-level or nested keys are counted, or what output format the count will take.

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 the schema has 100% description coverage, the parameter descriptions are mismatched with the tool purpose: url, city, feed, host, zone, and query appear to belong to other tools, and json is described as 'JSON text to validate' rather than the object whose keys are counted. The tool description adds no mapping between 'JSON object' and a specific 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 clear verb and resource ('Count keys in a JSON object') and somewhat distinguishes from validation tools, but it does not map that purpose onto any of the 9 optional parameters; the only JSON-related parameter is described as 'validate' rather than 'count', so the actual target is ambiguous.

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 for when to use this tool instead of siblings like validate-json, search-query-len, or file-path-ok. There is no mention of input constraints, prerequisites, or when not to use it.

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