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

With no annotations provided, the description must carry the full behavioral burden. It adds 'Values discarded', which clarifies that input values are ignored, but it does not disclose whether the operation is read-only, return format, potential errors, or side-effect behavior. The tool appears safe to invoke minimally, but transparency is incomplete.

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 entire description is two short, direct sentences: the purpose comes first, then a clarifying note about values. Every word earns its place and there is no fluff.

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, no output schema, and no annotations, the description is minimal. It clarifies 'Count keys' but does not specify what a response would look like, how zero-key input behaves, or why an agent would need this information. It is adequate for a very simple counting tool, but gaps remain.

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 parameters are already individually documented. The general statement 'Values discarded' does not add much beyond the per-parameter 'discarded' notes already in the schema. It does sum up the intent but offers no new meaning for any specific parameter.

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 verb and resource: 'Count keys in a JSON object. Values discarded.' It makes the core action obvious and the scope unambiguous once the input schema is seen. It does not name sibling alternatives, but the uniqueness of the operation is fairly clear from the name and description alone.

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?

The description gives no guidance on when to use this tool versus siblings like validate-json or domain-shape. There are no stated preconditions, alternate tool references, or exclusion rules, leaving selection to inference based mainly on the tool's distinct name.

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