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

With no annotations, the description carries the full burden, yet it only says values are discarded. It does not disclose whether the count is top-level or recursive, what happens with invalid JSON, what is returned, or whether the operation has side effects beyond discarding values.

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 concise and front-loaded: the action, 'count keys', appears in the first words. It is not padded, but it is terse enough that a bit more parameter guidance would have made it more useful.

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?

For a tool with nine unrelated-looking parameters, no output schema, and no annotations, this description is not complete enough. An agent cannot infer the required input, the expected return value, or error behavior from the one-line description, especially with the schema's conflicting json parameter description.

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 the schema descriptions cover all parameters, the tool description never identifies which parameter supplies the JSON object whose keys are counted. The closest candidate, json, is documented as validation input that is discarded after the check, which does not match the stated count-keys behavior and leaves the mapping ambiguous.

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 the keys in a JSON object. It is not a tautology, and 'Values discarded' adds a useful boundary, but it does not differentiate this tool from related JSON sibling tools such as validate-json.

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 validate-json, domain-shape, or other JSON-related siblings. 'Count keys' implies a use case, but no explicit context, exclusions, or alternative routing is provided.

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