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

With no annotations supplied, the description must fully disclose behavior. The only behavioral note is 'Query discarded,' indicating input is not retained, but it fails to mention output format, whether any parameters are ignored, or any side effects. For a tool with multiple input fields, this is insufficient 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 only two short sentences and front-loads the main action, but it is under-specified for the tool's complexity. The second sentence 'Query discarded' is useful, yet the overall description omits essential mapping and return information, so the brevity is not appropriate.

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 7 parameters and no output schema, the description is severely incomplete. It does not explain what the number of characters corresponds to, how the fields relate to the count, what the return value looks like, or when this tool is relevant. An agent would struggle to invoke it correctly without additional external knowledge.

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 has descriptions for all 7 properties, so schema coverage is high, but the overall description actively conflates the purpose by referencing a 'search query' that does not map to any property. The description adds no clarification on whether each field is counted separately, concatenated, or only one is used. This creates param ambiguity rather than resolving it.

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 verb and resource ('Count characters in a search query') but the input schema contains no parameter named 'query'—only generic fields like ref, url, city, feed, host, json, and path. An agent cannot identify which field represents the search query, making the purpose vague and potentially misleading. It does not distinguish itself from sibling tools beyond the generic counting action.

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 about when to use this tool versus any of the many siblings (e.g., domain-shape, validate-json, web-fetch). The description gives no context, prerequisites, or exclusion criteria, leaving the agent to guess the tool's role.

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