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

With no annotations, the description carries the full burden of behavioral disclosure. It reveals that values are discarded, which is useful, but it does not clarify whether nested keys are counted, what happens for invalid JSON, whether the operation is purely local, or what the result format is. This is too thin a behavioral picture for an agent to rely on safely.

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, front-loaded, and contains no filler; both sentences earn their place. It is economical to the point of omitting useful context, but those omissions are better penalized under contextual completeness rather 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?

For a tool with nine optional parameters, no required parameters, no output schema, and no annotations, a two-sentence description is inadequate. It does not identify which parameter holds the JSON object, what the returned count looks like, or how invalid input is handled. An agent would likely need to inspect sibling tools or experiment to invoke it correctly.

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?

Schema description coverage is 100%, so the baseline is 3. The description itself does not map 'JSON object' to the 'json' parameter, and the schema wording for json says 'validate' rather than 'count keys,' leaving a mild semantic mismatch. However, the schema already documents each parameter, so the description adds little but does not need to fully compensate.

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 specific verb and resource: 'Count keys in a JSON object.' It also adds a key distinguishing behavior by saying values are discarded, which separates it from validation or shape-checking tools like validate-json. It does not explicitly name a sibling or cover edge cases, but the core purpose is unambiguous.

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 about when to use this tool versus alternatives such as validate-json or domain-shape. The description does not state prerequisites, exclusions, or conditions that would make another sibling tool more appropriate. With 27 sibling tools, this absence is significant.

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