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

'Values discarded' gives some transparency about not retaining input values, and there are no annotations. However, the description does not state what the tool returns, how nested keys are handled, or what happens on invalid JSON, so the behavioral disclosure is incomplete.

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 concise and easy to parse, consisting of two short sentences. However, the overall structure is weakened by the large, unrelated input schema that is not reflected in the description.

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 nine optional parameters and no output schema, the description is not enough for an agent to reliably use the tool. It does not explain which parameter to populate, what 'keys' means (e.g., top-level vs nested), or what output format to expect.

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?

The schema has nine parameters, all optional, but their descriptions are unrelated to counting JSON keys. The only JSON-related parameter, 'json', says it is for validation and discarding after the check, which contradicts the tool's stated purpose of counting keys. No parameter clearly represents the JSON object to be counted.

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 action and resource ('Count keys in a JSON object') and adds that values are discarded. However, it does not map to any input parameter; the schema has a 'json' parameter whose description says 'validate' rather than 'count', so the actual purpose is unclear from the full tool definition.

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 that it should be used for counting JSON keys rather than validating JSON or other related operations, and no exclusions or context are provided.

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