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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description still earns credit for disclosing the short-lived URL and expiration_seconds, and for stating that the tool returns a URL rather than file bytes—context that drives how the agent must handle the result.

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?

Five short sentences, purpose front-loaded, with no filler. The handling instructions are dense with value, though the phrasing is slightly prescriptive/repetitive around saving versus viewing.

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 read-only single-page fetch with a full schema and an output schema, everything the agent needs is present: what comes back, that it expires, and what to do with it. Nothing essential is left to inference.

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 fax_id, user_id, and page_num are all documented in the schema, including the 1-based indexing and the 'default: self' for user_id. The description adds no parameter-level detail beyond 'one fax page', 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?

The description names a specific verb and resource—'Return a short-lived URL for one fax page as a one-page PDF'—and pins down both the returned artifact (URL, not bytes) and the format (one-page PDF). That is enough to separate it from get-file, get-fax, and get-fax-thumbnail 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?

It gives concrete operational direction: save the URL to disk immediately, don't paste page bytes into the conversation, and open the saved PDF when the user wants to view it. What's missing is an explicit routing rule—when to reach for this instead of get-file or get-fax-thumbnail—so the agent still has to infer the alternative.

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