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

Annotations already establish readOnly, idempotent, and non-destructive behavior, so the description adds value by disclosing that it runs keyless over the tunnel and by explaining the returned entry metadata. This is meaningful beyond what the annotations and schema provide.

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?

Two concise sentences: the first states the core action, and the second adds output shape and the keyless tunnel context. Every sentence earns its place, with no filler or redundant restatement of the schema.

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 list operation, the description plus schema covers required inputs, return fields, and connection/auth behavior. There is no output schema, but the description compensates by enumerating the returned entry properties. Error or permission edge cases are not mentioned, but they are not essential for selecting and invoking this tool.

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 100%, so the schema already documents host, path, and username including defaults. The description does not add parameter-level meaning beyond the schema, which warrants the baseline score of 3.

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 ('List a directory') on a specific resource ('one of your servers over SFTP'), and it spells out the returned fields: name, directory flag, size, and modified time. This clearly differentiates it from siblings like sftp_read and sftp_write.

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 useful selection context by noting it is keyless over Termalin's tunnel and explicitly comparing it to ssh_exec. It does not state hard exclusions or decision rules versus sftp_read/sftp_write, but the listing behavior and return format make the intended use clear.

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