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

With no annotations, the description carries the behavioral disclosure burden. It only says 'Query discarded', which is already present in the query parameter's schema description. It does not state what the tool returns, whether it has side effects, or that only the 'query' parameter is relevant among the 9 optional inputs.

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 extremely short and front-loaded, containing exactly two purposive sentences. There is no fluff or repetition, which earns full marks for conciseness.

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 accepts a large schema with 9 optional parameters and no output schema. The description does not explain why so many parameters are present, which of them are actually used, or what the output format is when characters are counted. This ambiguity makes the description insufficient for the complexity level of the input schema.

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%, and the description adds little beyond what the schema already says for 'query'. It does not clarify the relationship among the large set of optional parameters, so it stays at the baseline.

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 the verb 'Count' and the resource 'characters in a search query', giving the primary intent. However, it does not differentiate from sibling length-related tools like hn-front-count or memory-key-count, so it only reaches a 4.

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 or when not to. It does not mention alternatives or any context like 'use this only when you need to check query length', so the agent receives no usage direction.

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