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

The description adds one useful behavioral note: 'Query discarded,' indicating the input is not retained. With no annotations at all, however, it does not disclose what is returned, how empty or multi-field inputs are handled, or how characters are counted. This is better than nothing but still leaves important behavioral details unstated.

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 two short sentences, both of which earn their place: the first says what the tool does, and the second states the side-effect. It is front-loaded with the core action and contains no filler or redundancy.

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?

With no output schema and no annotations, the description should specify what the tool returns and which parameter actually drives the operation. It does neither explicitly, and with nine optional parameters the ambiguity is meaningful. The description is adequate for a trivial utility but not complete enough for reliable agent invocation.

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?

The schema description coverage is 100%, so all nine parameters are already described in structured form. The description does not add meaning beyond the schema's own description of 'query' as 'Search text; discarded after the length check.' The word 'query' ties the description to one parameter, but it does not explain the other eight accepted parameters or clarify whether they are ignored.

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 characters in a search query.' This clearly describes what the tool does and distinguishes it from more shape- or status-oriented sibling tools. It does not explicitly explain that the relevant input is the 'query' parameter, but the tool name and the 'Query discarded' phrase make that link reasonably clear.

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 use this tool versus alternatives such as memory-key-count or other validation/checking tools. The description gives no context, exclusions, or conditions under which an agent should prefer this tool, leaving usage entirely to inference.

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