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

Since no annotations are provided, the description carries the full burden for behavioral disclosure. It only says 'Values discarded,' but does not explain output format, how invalid JSON is handled, whether nested keys are counted, or whether the tool has any side effects.

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 and front-loaded with the main verb, but it is too terse to compensate for the mismatch with the schema. It does not earn full marks because it omits essential information about which parameter to use and what output to expect.

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 a 9-parameter schema with no required fields and no output schema, the description is inadequate for an agent to reliably select and invoke the tool. It does not explain how the optional parameters relate to the operation, what counts as a key, or what the tool actually returns.

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 descriptions cover all 9 parameters, they are clearly copied from other tool contexts (e.g., 'JSON text to validate', 'File path to check') and do not align with the stated purpose of counting keys. The 'json' parameter may be intended, but its description contradicts the tool's purpose by saying 'validate' instead of 'count keys', and the other parameters are irrelevant distractions.

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 in a JSON object') and distinguishes it from sibling tools like validate-json, but it does not specify which input parameter contains the JSON object. The schema includes nine unrelated optional parameters, so the mapping from description to input 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?

The description provides no guidance on when to use this tool versus alternatives. It does not mention any preconditions, exclusions, or comparison to sibling tools such as validate-json or search-query-len.

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