count_chars_file

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

With no annotations, the description carries the burden of behavioral disclosure. It provides useful behavioral detail by specifying UTF-8 encoding and the Unicode code point counting semantics, but it does not mention error behavior for invalid UTF-8, missing files, or whether newlines are included. This is adequate for a simple read operation but not exhaustive.

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 lines long, front-loads the core behavior, and contains no filler. The 'Args' clarification about absolute paths earns its place by guiding correct invocation.

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?

For a simple one-parameter counting tool with an output schema available, the description covers the necessary input semantics and the key counting behavior. It does not describe edge cases or error handling, but those are relatively minor for this tool's complexity.

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 0%, so the description must compensate. It does by documenting file_path as an absolute path, which adds meaningful constraint beyond the schema's bare 'File Path' string type. This is sufficient for the tool's single parameter.

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 verb ('Count') and resource ('UTF-8 file'), and clarifies that it counts Unicode code points rather than bytes or lines. This clearly differentiates it from sibling tools like count_tokens_file, count_lines_file, and count_kb_file.

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 purpose implies when to use this tool — when a Unicode code point count of a file is needed — but it does not explicitly mention alternatives or state conditions for choosing another sibling tool. Usage guidance is implied rather than stated.

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