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

With no annotations, the description carries the behavioral burden. 'Query discarded' is a useful disclosure that input is not retained, and the operation is clearly non-mutating. However, it does not explain the output format, whether other accepted parameters are ignored, or any edge-case behavior.

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 with no wasted words, and the core action is front-loaded. It could be slightly more informative without becoming verbose, but as written it is appropriately concise.

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?

The tool has 9 optional parameters, no output schema, and no annotations, yet the description does not explain which parameter to use or how the other parameters relate to the tool. An agent may infer 'query' from the schema, but the presence of many unrelated fields is confusing. The description is not sufficient for fully confident 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?

Schema description coverage is 100%, so the baseline is 3. Every parameter already has a description, and the 'query' parameter explicitly says 'Search text; discarded after the length check.' The tool description itself adds no additional parameter semantics beyond confirming the query focus.

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 clearly states a specific action and resource: 'Count characters in a search query.' This distinguishes it from sibling shape-checkers and URL validators. It is not fully explicit about which parameter holds the search query or that the return value is the length, but the tool name and schema disambiguate.

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 about when to use this tool versus alternatives such as memory-key-count or hn-front-count. The description implies a character-count use case but does not state when-not-to-use it or mention any sibling tools. An agent receives no routing help.

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