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

There are no annotations, so the description carries the full burden. It discloses that values are discarded, but does not explain output format, side effects, error behavior, permissions, or what happens with ignored parameters. This is insufficient for an unannotated tool.

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 short and free of fluff, but the brevity sacrifices critical details. There is no structure or organization, and the two sentences do not convey how to invoke the tool correctly.

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 definition is severely incomplete: no output schema, no examples, no error behavior, and no relationship to sibling tools. With nine optional parameters and no required parameter, an agent cannot determine what input to provide.

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?

All nine parameters are optional strings, and none is clearly identified as the JSON object whose keys are counted. The 'json' parameter description says 'validate; discarded after the check', which contradicts the tool's stated purpose. Other parameters (city, url, timezone, query) appear copied from unrelated tools and are actively misleading.

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 operation ('Count keys') and target ('JSON object'), but the input schema exposes nine unrelated string parameters, making it unclear which parameter contains the JSON object. It does not distinguish itself from sibling tools like validate-json or search-query-len beyond the verb.

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 such as validate-json or search-query-len. There are no conditions, prerequisites, examples, or explicit 'use when' instructions; only the minimal hint that values are discarded.

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