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

With no annotations, the description carries the behavioral burden. It explicitly says values are discarded, which signals a pure read-only count and tells callers that value content can be ignored. However, it does not state the return format, malformed-input behavior, or whether key counting is recursive, so transparency is adequate but not complete.

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?

Two short sentences, action first, with no filler. 'Values discarded' carries meaningful behavioral information beyond the schema. It is appropriately concise, though the brevity leaves important invocation details uncovered.

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?

No output schema, no annotations, and nine optional parameters mean the description needs to provide more invocation guidance. It does not explain the return value, how to identify the JSON object among the parameters, or key-count scope. The definition provides the gist but not enough to ensure correct use.

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?

Although every parameter is documented in the schema, the description never maps 'JSON object' to a specific parameter such as `json`. The schema itself describes `json` as 'JSON text to validate', which conflicts with the count-keys purpose, and with nine optional parameters the caller cannot reliably know which argument to pass.

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 operation ('Count keys') on a specific resource ('a JSON object') and adds that values are discarded, which distinguishes it from siblings like validate-json. It does not specify nested vs top-level keys or how the object is supplied, but the core intent 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?

There is no when-to-use or when-not-to-use guidance and no mention of alternatives, despite many sibling tools. The only usage signal is implied by the name and one-line description; no exclusions, prerequisites, or comparisons are given.

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