char_info

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It explicitly indicates this is a read-only info operation, lists exactly what information is returned, and notes that it processes each character in the input. It does not discuss error handling or rate limits, but for a simple info tool, this is adequate and adds value beyond the schema.

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 a single sentence that efficiently conveys the tool's purpose and output. The leading '[PRO — 3 trial uses left]' is extraneous to the tool's function but does not significantly detract from clarity, meriting a 4.

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 is simple, with one parameter and no output schema. The description covers all relevant aspects: what the tool does, what information it returns, and that it operates per character. The input length is documented in the schema, and there are no undocumented side effects, making it sufficiently complete.

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 schema already provides a complete description of the single 'text' parameter, including its type and length constraint (1-20 chars). The description does not add any additional semantic details about the parameter itself, so the 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 uses the specific verb 'Get' and clearly identifies the resource as 'Unicode character info' with a defined scope ('for each character in the input'). It enumerates the specific data fields (codepoint, name category, UTF-8 bytes, HTML entity), which distinguishes it from any sibling tool.

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 provides clear context for when to use the tool: whenever a user needs Unicode character details. It does not explicitly name alternatives or exclusions, but the sibling tools (e.g., base64, hash, uuid) have no functional overlap, making the intended usage unambiguous.

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