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

Because no annotations are present, the description must cover behavioral traits. It does add 'Values discarded,' which hints at a read-only operation, but it does not state side effects, how empties are handled, or whether it persists anything. For a tool with no annotation support, this is minimal disclosure.

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 consists of two short sentences, 'Count keys in a JSON object. Values discarded.' Both earn their place with no redundancy, making it exceptionally concise and front-loaded.

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 parameters, no required fields, no annotations, and no output schema, the description needs to explain the input mapping and expected result. It neither specifies which parameter to use nor what happens with no parameters, leaving the tool incomplete for correct invocation.

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 schema clearly documents all nine parameters, and the baseline is 3. The description adds no additional meaning about which parameter is the JSON object or how the other parameters relate, so it does not exceed the schema-heavy baseline.

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'), which is clear. However, it does not differentiate from sibling tools more to its ambiguity about which of the nine parameters carries the object, but it is not a tautology.

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 when-to-use or alternative guidance is provided. The description does not mention other tools, prerequisites, or contexts where this is appropriate, and the many unrelated parameters (url, city, zone) are not tied to the stated purpose.

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