ftp_size

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 only states the purpose and does not disclose important behaviors such as whether it returns the size in bytes, what happens if the file does not exist, how errors are handled, or whether it works for directories. For a read operation, some of this may be assumed, but the lack of any behavioral detail leaves significant ambiguity.

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, concise sentence: 'Get the size of a file on FTP server.' It is front-loaded with the action and contains no unnecessary words. Every word earns its place, making it highly efficient.

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?

This is a simple tool with one parameter and no output schema, but the description fails to explain what the tool returns or how to handle errors. The agent is left without knowing whether the size is in bytes, kilobytes, or a formatted string, and whether it returns an error if the path is invalid. Without annotations or an output schema, this gap makes the description incomplete for reliable invocation.

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 has 100% coverage for the single parameter 'path' with a clear description ('Remote path on the FTP server'). The tool description adds no additional meaning beyond the schema, so the baseline score of 3 is appropriate. The schema does the heavy lifting for parameter understanding.

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 tool's action: 'Get the size of a file on FTP server.' It uses a specific verb ('get') and resource ('size of a file'), making it distinct from sibling FTP tools like ftp_list or ftp_download. The purpose 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 intended use is implied by the description: call this tool when you need the size of a specific file on an FTP server. However, there is no explicit guidance on when not to use it or alternatives (e.g., ftp_list might show sizes in directory listings). The simplicity of the operation makes the usage fairly obvious, but it lacks explicit exclusionary or comparative guidance.

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