Format a file

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

The annotations already indicate a non-read-only, idempotent, and non-destructive tool. The description adds meaningful behavioral context by explicitly stating that the file is saved after formatting, which is not derivable from the annotations alone. No contradiction with annotations.

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, well-structured sentence that front-loads the action and resource. It contains no filler or redundant information and earns its place entirely.

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 tool's moderate complexity, the description covers the essential aspects: scope (whole file or range), the action (format and save), and the formatter context. The schema and annotations cover the remaining details, and an output schema is absent so return values do not need explanation. It is 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 input schema provides descriptions for all parameters (100% coverage), so the description does not need to explain parameters in detail. It does add a slight contextual hint about whole file vs. range, but this adds minimal value over the schema.

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 clearly states a specific action ('Format') on a specific resource ('a whole file or a line range') and additionally notes that it saves afterwards. It distinguishes itself from sibling tools by focusing solely on formatting, which is unambiguous.

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: formatting either an entire file or a specific line range. It does not, however, explicitly exclude alternatives or name sibling tools like nvim_code_actions that might also be able to format, so it falls short of a 5.

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