count_tokens_file

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

With no annotations available, the description carries the burden of behavioral disclosure. It does add useful details: the file must be UTF-8, and an empty model defaults to ANTHROPIC_TOKEN_COUNT_MODEL. It does not describe what happens with invalid paths, encoding errors, or file-size limits, but for a straightforward read-only counting operation this is acceptable. The description adds some behavioral context without being 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 tight and front-loaded: a one-line purpose followed by an Args section. There is no filler, and each sentence adds value. It covers both parameters and the default behavior without unnecessary elaboration, making it easy for an agent to parse quickly.

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 two-parameter tool, the description covers the essential inputs and default behavior. The output schema exists, so return-value documentation is not required from the description. However, it lacks guidance on error conditions, what constitutes a valid UTF-8 file, and how to choose between this and sibling counting tools, leaving moderate gaps for an agent that lacks prior context.

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, and it does meaningfully. It clarifies file_path must be an absolute path, and it explains model as 'Model or encoding name' with an explicit default behavior. Both parameters are given semantic meaning beyond their names, types, and defaults, making the tool usable without inspecting external documentation.

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 action ('Count tokens') on a specific resource ('a UTF-8 file'), which is immediately distinguishable from sibling tools like count_tokens_folder, count_lines_file, count_chars_file, and count_kb_file. The file path parameter and encoding qualifier make the scope explicit. Unlike a vague 'Process' definition, this gives an agent a clear understanding of what the tool does.

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 implies the tool should be used when a token count for a file is needed, and the sibling list provides alternative counting tools. However, there is no explicit guidance on when to prefer this over count_tokens or count_tokens_folder, nor any exclusions for non-UTF-8 files or other edge cases. Usage context is present but left largely to inference.

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