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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds value by explicitly stating 'Side effects: none (read-only)' and disclosing that the return is a base64 PDF in structured output, which is behavioral context beyond the annotations. No contradiction with annotations.

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 sentences with zero waste. The core action and format are front-loaded, and the side-effect note is concise. Every sentence earns its place.

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's simplicity, the annotations cover safety, the schema covers parameters, and the output schema exists, the description is nearly complete. The only minor gap is not explaining when to use this over get-fax or get-fax-thumbnail, but the output schema and annotations fill most contextual needs.

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 the schema already documents both parameters. The description does not add extra meaning about fax_id or user_id beyond what the schema provides, but it does not need to; the baseline of 3 applies because the schema carries the burden.

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 states a specific verb ('Retrieve') and resource ('fax confirmation report (PDF)'), clearly distinguishing it from siblings like get-fax, get-fax-thumbnail, and list-faxes. The parenthetical format note adds precision without ambiguity.

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 implies usage context (retrieving a confirmation report for a fax) but does not explicitly state when to prefer this over get-fax or get-fax-thumbnail, nor does it mention any exclusions. The read-only note and PDF format hint at the use case, but no explicit alternatives or conditions are given.

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