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

With no annotations present, the description carries the behavioral disclosure burden. 'Query discarded' usefully signals that the input is not retained and the operation has no lasting side effects, but the description does not state the return format, edge-case behavior, or whether only the 'query' parameter is considered. This is partial but not complete transparency.

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, and contains no filler or redundancy. It loses a point only because it is so terse that it omits useful context about the oddly large parameter list and expected return, though every sentence it does include earns its place.

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 counting tool, the description plus rich schema is mostly sufficient: the agent can infer it should pass 'query' and receive a character count. However, with no output schema, no annotations, and nine parameters that are mostly irrelevant to the stated purpose, a more explicit statement about return value and ignored parameters would make the tool fully self-contained.

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?

All 9 parameters already have description text in the input schema, giving 100% schema description coverage, so the baseline applies. The tool description adds no extra parameter-level meaning beyond identifying the query as the search text, and the schema itself already documents that 'query' is discarded after the length check.

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 ('Count characters') and resource ('a search query'), so an agent can tell what the tool does without opening the schema. It does not explicitly distinguish this tool from sibling count-related tools, but the name and wording are unambiguous enough to earn slightly less than top marks.

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 alternatives, and it names no sibling tools or exclusion conditions. The only implied usage is 'when you need to count characters in a search query', but no explicit 'use this instead of X' context is provided.

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