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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the line 'Side effects: none (read-only)' merely restates structured data. The description adds no behavioral context beyond annotations — nothing about pagination, ordering, or what pending states are included.

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 short lines, front-loaded with the core purpose and no filler. The remaining line is redundant with annotations but costs almost nothing in length.

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?

With an output schema present and complete annotation coverage, plus a fully described optional parameter, the description is close to sufficient. Slight gap: no statement of ordering/limits on the returned list, which an agent might need.

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% and the single user_id parameter ('Default: self') is fully documented in the schema. The description adds no meaning about the parameter, which is acceptable at baseline when the schema does the work.

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?

States a specific verb and resource ('List faxes in the outbox') plus a qualifying scope ('waiting to be sent'), which clearly separates it from list-faxes (sent faxes) and get-outbox-fax (single item). It never names a sibling explicitly, so distinction relies on the reader inferring from scope.

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 phrase 'waiting to be sent' implies when you'd call it (checking pending items), but there is no explicit when-to-use guidance and no mention of alternatives such as get-outbox-fax for a single item or list-faxes for sent history. Usage is only inferable.

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