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

The only disclosed behavior beyond the name is 'Query discarded,' which signals an ephemeral operation. With no annotations, the description carries the full burden, but it does not explain output format, how characters are counted, what happens with a missing query, or why the schema contains nine unrelated optional parameters.

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 short, front-loaded with the main verb, and contains no filler. It could be more informative, but it is not bloated or repetitive.

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 nine optional parameters and no output schema, this description is too sparse to support correct invocation. It does not state which parameter to provide, what the return value is, or whether the extra schema fields are accepted and ignored or should not be used.

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 documented individually and the description need not repeat them. However, the description does not clarify that the 'search query' corresponds to the `query` parameter or explain the role of the other eight parameters.

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 a specific object ('a search query'), so an agent can understand the core purpose. It does not explicitly differentiate this from sibling tools such as domain-shape, normalize-url, or validate-json, which also perform measurement/validation-like checks.

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 choose this tool instead of one of the many shape-check or validation siblings. There is no mention of prerequisites, exclusions, or a preferred context, so the agent must infer when this tool is appropriate.

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