append_file

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

No annotations are provided, so the description carries the full burden. It discloses the mutation (append), the create-if-missing behavior, the encoding default, and the return dict structure. It does not mention error handling or permission issues, but for a simple file operation this is adequate.

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 structured as a clear docstring with a summary, args, returns, and examples. It is slightly verbose with the Args/Returns layout, but every section adds value, and the examples are helpful without being excessive.

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 description covers the tool's purpose, all parameters, return format, and includes examples. The tool is simple, and the description provides everything needed to invoke it correctly. No critical information is missing.

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 provides only types and defaults, with 0% description coverage. The description compensates by describing each parameter: 'path: Path to the file', 'content: Content to append', 'encoding: File encoding. Default: "utf-8"'. It also supplies usage examples, fully clarifying parameter roles.

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 the action: 'Append content to an existing file (or create it if it does not exist).' This uses a specific verb and resource, and the 'create if not exists' detail distinguishes it from overwrite-style tools like write_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 description gives clear context for usage by explaining the append-or-create behavior, but it does not explicitly name alternatives or exclusions. It implies when to use it (e.g., when you want to preserve existing content) without directly contrasting with write_file.

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