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

"Side effects: none (read-only)" merely restates readOnlyHint/destructiveHint from the annotations, adding no new information. "Returns paginated results" is mild behavioral value, but pagination mechanics (limit/offset/cursor) are already in the schema and the output schema covers the response. Nothing about permissions, per-user scoping semantics, or the default-to-self behavior is explained.

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 sentences, front-loaded with the core action, no filler prose. The safety line is the only expendable sentence given the annotations already carry it.

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?

A 15-parameter filtered-list tool with an output schema and full schema coverage is adequately served by its structured fields, so the description need not enumerate filters. But it omits the one thing structured data cannot convey: the inbox/sent/spam category scoping that separates this from the outbox sibling, leaving a real ambiguity.

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 every one of the 15 parameters (filters, ordering, date bounds, page counts) is already documented at the field level. The description adds nothing beyond that, which is acceptable but not additive; 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?

States a specific verb and resource ("List fax records for a user") so the operation is unambiguous. However, it never distinguishes this from the sibling list-outbox-faxes, which is the most likely source of misfires. Clear but not sibling-differentiated.

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?

No guidance on when to use this versus list-outbox-faxes, get-fax, or get-fax-report. The only implied routing signal is the required `category` enum in the schema, which the description never mentions. An agent must infer scope from schema alone.

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