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

With no annotations, the description carries the full burden. It only states 'Query discarded,' which discloses that the query is not retained, but it does not mention the return format (whether a number or boolean), whether other parameters are also discarded, or if there are any side effects. This is insufficient for an agent to predict 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 fluff. It is concise and front-loaded with the core action. However, it is under-specified, but that is a completeness issue, not a structure issue.

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?

Given the complexity (9 parameters, no output schema), the description is incomplete. It does not specify what the tool returns (e.g., a count, a boolean), nor does it clarify which parameter is the 'search query' or how the other parameters factor in. An agent would struggle to call this tool correctly without opening the schema and inferring intent.

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 each parameter is already documented in the schema. The tool description adds no extra meaning about parameters beyond repeating the query concept. Since the schema does the heavy lifting, a baseline of 3 is appropriate.

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 clear verb and resource: 'Count characters in a search query.' However, the input schema includes 9 unrelated optional parameters (ref, url, city, feed, host, json, path, zone) alongside 'query', and the description gives no hint about how these relate to the stated purpose. An agent cannot tell if the tool accepts any of these strings or only 'query'.

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 provided on when to use this tool versus alternatives like yaml-key-count or memory-key-count. The description and name imply it is for search query length, but no explicit context or exclusions are given.

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