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

With no annotations, the description must carry the full burden of behavioral disclosure. It does state that 'Values discarded' – a useful trait – but fails to mention side effects, required permissions, reversibility, or what happens with the many optional parameters. For a tool with 9 parameters, this is a significant gap.

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 a single sentence with zero redundancy. It is front-loaded with the core action and includes a behavioral note. Perfectly concise.

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 9 optional parameters but the description does not explain how they relate to the stated purpose of counting keys in a JSON object. There is no output schema, so return value is unexplained. The disconnect between the short purpose and the wide parameter set leaves an agent without enough context to call 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 each parameter already has a description. The tool description adds 'Values discarded' which aligns with the per-parameter notes like 'discarded after the shape check'. However, the description does not clarify which parameter is the primary input (e.g., 'json' vs 'ref') or how the other parameters relate to counting keys. It adds marginal value beyond the schema.

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 action: 'Count keys in a JSON object' with a resource (JSON object). It is a distinct verb+resource combination. However, it does not differentiate itself from sibling tools like validate-json or hn-front-count, which also deal with JSON objects or counting. The name 'memory-key-count' suggests a memory context not captured in the description.

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 on when to use this tool versus the many siblings. There is no mention of alternative tools, prerequisites, or scenarios where this tool is preferred. The description provides no context for selecting it over others.

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