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

With no annotations provided, the description carries full responsibility for disclosing behavior. It only mentions that values are discarded, but says nothing about error handling, invalid JSON behavior, side effects, or the nature of the count output. This is critically insufficient for a tool with 9 parameters.

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, which is concise, but it is under-specified for a tool with 9 parameters and no output schema. Conciseness is not effective when essential details like input selection and output format are missing.

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 is moderately complex (9 parameters, no output schema, no annotations), yet the description provides almost no context: it doesn't state which parameter is the JSON, what the return value looks like, how errors are handled, or when it should be used. The description is grossly incomplete.

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 baseline is 3, but the tool description adds no clarification about which parameter to use for the JSON object. The 'json' parameter description says 'validate', which contradicts the counting intent, and the tool description does not resolve this ambiguity. Thus the description fails to add 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 states a clear action ('Count keys in a JSON object') but does not specify which of the 9 input parameters holds the JSON text, nor does it differentiate from sibling tools like validate-json that also handle JSON. The purpose is ambiguous despite a concrete verb.

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 guidance on when to use this tool versus alternatives. No mention of scenarios, exclusions, or context where counting keys is preferred over validating or other operations.

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