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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior. The description adds useful behavioral context: results are paginated, and the agent should summarize results in plain language rather than dumping raw API metadata. This goes beyond the annotations without contradicting them.

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?

The description is short and front-loaded with the core action, followed by pagination and user-handling guidance. Every sentence adds some value, though 'Side effects: none (read-only)' largely repeats what the annotations already state.

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?

Given the rich input schema, annotations, and the presence of an output schema, the description is sufficiently complete. It covers pagination and response presentation behavior, which are the main things not already encoded in structured metadata. A short note on when to prefer this over list-outbox-faxes would make it fully complete.

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?

The input schema has 100% parameter description coverage, so the schema already documents all 15 parameters. The description adds only the high-level 'for a user' framing, which hints at user_id but does not substantially extend the schema's parameter explanations.

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 clearly names the action and resource: 'List fax records for a user' and adds that results are paginated. This is specific enough to identify the tool's purpose, though it does not explicitly distinguish it from the sibling tool list-outbox-faxes.

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 no guidance on when to use this tool versus alternatives such as list-outbox-faxes or get-fax. It implies usage by naming what it does, but lacks exclusion criteria, prerequisites, or alternative routing.

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