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 says 'Values discarded' without explaining error handling, return format, side effects, or the fact that the tool accepts multiple parameters that are ignored. This is insufficient for a tool with such a broad schema.

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 extremely short (two sentences), which is concise, but it omits essential information about parameter selection and behavior. It is under-specified rather than appropriately concise, and the information is not structured in a way that aids an agent.

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 9 optional parameters and no output schema, the description is grossly incomplete. It does not explain which parameter is the JSON input, what happens if multiple are provided, or what the count result looks like. An agent cannot confidently call this tool based on the given information.

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 coverage is 100%, so all parameters have descriptions. However, the tool description does not clarify which parameter holds the JSON object to count, nor does it explain why other parameters are present. The baseline of 3 is appropriate because the schema does the heavy lifting, but the description adds no semantic 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 specific action ('Count keys in a JSON object') but the schema exposes 9 unrelated parameters (url, city, feed, host, zone, query, etc.) that have no obvious connection to JSON key counting. This creates ambiguity about what the tool actually does, and it does not differentiate from siblings like validate-json or search-query-len.

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 alternatives. There is no mention of use cases, exclusions, or which sibling handles similar scenarios. The description only states a bare operation without any contextual routing.

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