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

There are no annotations, so the description carries the full behavioral burden. It does disclose an important behavioral trait, 'Values discarded,' implying a pure read/compute operation with no storage of values. It does not state behavior on invalid JSON, whether keys are top-level or recursive, or what the output format is.

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 two short, front-loaded sentences with no filler. Both sentences add value: the purpose and the fact that values are discarded.

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?

The tool has nine parameters and no output schema, yet the description does not say which parameter contains the JSON object, what the return value is, or whether the many discarded parameters are meant to be ignored. The schema descriptions also seem mismatched, especially the json field describing validation rather than counting, leaving the agent without enough context to invoke the tool confidently.

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?

Input schema coverage is 100%, so the schema already documents all parameters. The description adds almost no parameter-level meaning beyond the schema and does not explicitly identify the json parameter as the one to populate. Baseline 3 is appropriate because the schema handles parameter documentation.

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 clearly states a specific verb and resource: count keys in a JSON object. It also communicates a key differentiator, that values are discarded, which sets it apart from validation or transformation tools. It is not a 5 because it does not explicitly distinguish it from sibling validate-json and leaves ambiguity about whether nested keys are counted.

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 intended usage is implied: use this when you need the number of keys in a JSON object rather than validation, fetching, or normalization. However, there is no explicit when-to-use or when-not-to-use guidance, and no alternative sibling tool is mentioned.

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