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

No annotations are present, so the description carries the full behavioral burden. It does disclose that the query is discarded, which is a useful privacy/retention detail, but it does not state the return format, whether other parameters are ignored, or any potential side effects. The disclosure is helpful but incomplete.

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, front-loaded sentences with no redundant wording. The first sentence states the operation, and the second adds a meaningful privacy/retention note.

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 nine optional parameters, no annotations, and no output schema, this description is incomplete. It does not identify which parameter is the operative one (the schema does), does not describe the return value, and leaves the presence of eight unrelated parameters unexplained.

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 input schema already provides 100% description coverage for all nine parameters, including 'Search text; discarded after the length check' for the query parameter. The description adds no parameter-specific meaning beyond the schema, so the baseline of 3 applies.

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') applied to a specific resource ('a search query'), which clearly distinguishes it from sibling count/shape tools such as memory-key-count and web-fetch. The tool name reinforces the same purpose.

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 intended use is implied: call this when the user needs the character count of a search query. However, there is no explicit statement of when not to use it, no mention of alternatives, and no exclusions beyond the narrow scope implied by the name.

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