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

Annotations already declare readOnly, idempotent and non-destructive, so safety is covered; the description adds real behavioral constraints beyond that — the 512 KB ceiling and the refusal of binary files, which are enforced limits an agent must plan around. It does not discuss permission/escalation behavior when the tunnel user or username lacks read access, which is the main remaining gap.

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 sentences, zero filler, with the core purpose and the size/content limit front-loaded before the alternative-tool routing. Nothing is padded.

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 3-parameter read tool with full schema documentation and no output schema, the description supplies everything needed: what is returned (contents), the input limits, and where to go when those limits are hit. Read-only safety is already carried by annotations.

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 coverage is 100%, so host, path and username are already documented with defaults and formats in the schema. The description adds no parameter-level detail (e.g. path normalization or username override semantics), so the baseline 3 applies.

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?

Specific verb+resource ('Read a text file ... over SFTP and return its contents'), plus an explicit scope boundary (text only, under 512 KB) that separates it from generic exec tools. An agent can distinguish it from ssh_exec and sftp_list without opening any schema.

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?

States the condition that disqualifies this tool (binary or >512 KB files) and names the alternative to use instead (ssh_exec with sed/tail). This is explicit when-not plus a named alternative, not inference.

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