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

The description adds behavioral context beyond annotations: it states 'Side effects: none (read-only)' which aligns with the readOnlyHint and destructiveHint annotations, and it instructs the agent to summarize results in plain language and avoid dumping raw API metadata. This is valuable guidance on how to present output, exceeding what annotations convey.

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 two sentences long, with the core purpose stated first and the behavioral guidance second. Every sentence earns its place—no redundancy, no fluff. It is front-loaded with the most important information, making it easy for an agent to scan.

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 tool has 15 parameters and an output schema, the description is appropriately complete. It covers the essential action, scope, pagination, and presentation behavior. The schema handles parameter details, and the output schema covers return structure. The description does not need to enumerate every filter; it provides just enough context for correct invocation.

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 all 15 parameters are documented in the schema. The tool description adds no parameter-specific meaning—it only mentions 'for a user' and 'paginated', which are not tied to any individual parameter. Given the high schema coverage, a baseline score of 3 is appropriate.

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 states the action (list) and resource (fax records) and scope ('for a user'). It also specifies that results are paginated, which adds clarity. However, it does not explicitly differentiate from siblings like list-outbox-faxes, though the distinct purpose is inferable.

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 provides no guidance on when to use this tool versus alternatives such as list-outbox-faxes, get-fax, or delete-fax. It does not state prerequisites, exclusions, or conditions that would steer the agent to a different tool. The only usage hint is about output formatting, not tool selection.

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