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

No annotations are present, so the description carries the burden. It reveals that values are discarded, which is a small behavioral hint, but it does not disclose error handling, what happens with invalid JSON, or any side effects. The schema parameter descriptions like 'discarded after the shape check' are inconsistent with the counting purpose, adding confusion.

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 extremely short, but it lacks essential information about how to invoke the tool. It is not efficiently front-loaded; it omits the critical link between the JSON object and the parameters. Every sentence is minimal but not earning its place because it does not convey usable guidance.

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 9 optional parameters, no required inputs, no output schema, and no annotations, the description is drastically incomplete. It fails to explain how any parameter feeds into the counting operation, making the tool effectively uncallable without external knowledge. The complexity demands far more detail than provided.

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?

Despite 100% schema coverage, the parameter descriptions do not align with the tool's purpose. The 'json' parameter is described as 'JSON text to validate' rather than as input for counting keys, and the other 8 parameters appear unrelated. The description does not clarify which parameter is the target, so the agent cannot map inputs correctly.

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 (count keys in a JSON object) but fails to specify which parameter provides the JSON input. It does not differentiate from siblings like validate-json, which also deals with JSON. The phrase 'Values discarded' adds minor detail but leaves the core usage 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 on when to use this tool versus alternatives. There are no exclusions or conditions, and the agent is left to infer from the name alone. No mention of prerequisites or preferred scenarios.

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