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

With no annotations, the description carries the behavioral burden. 'Query discarded' explicitly discloses that the input is not persisted, which is useful. However, it does not describe the return value, error behavior, or whether the other eight optional parameters are ignored, leaving some behavioral gaps.

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?

Two short sentences with no filler; the function is front-loaded and the behavioral note adds value without bloat. This is an appropriately sized description.

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 simple count operation the description plus fully documented schema is mostly usable: an agent can pass `query` and expect a character count. But with no output schema, no annotation, and nine optional parameters of which only one is relevant, the description does not fully clarify what is returned or that the other parameters are irrelevant.

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 schema already documents every parameter. The description maps 'search query' to the `query` parameter but adds no details about the other eight optional fields or how they relate to the tool, so it stays at the schema-covered baseline.

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 characters') and identifies the resource ('a search query'), which is enough to understand the core function. It does not differentiate it from sibling count/shape tools such as memory-key-count or hn-front-count, so it stops short of a 5.

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 about when to choose this tool instead of a sibling shape checker or other count tool. No context, exclusions, or alternatives are mentioned; the agent must infer usage solely from the name and first sentence.

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