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

The annotation already declares readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds one useful detail beyond that: the return value is a base64 PDF in structured output. This is genuinely non-trivial and helps an agent interpret the result, but there is no additional behavioral depth (e.g., errors, auth requirements), so with annotation coverage already in place, a mid-score is appropriate.

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 no waste. The primary purpose is stated up front, and the side-effect and return-format note follows without redundancy. 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?

The tool is a simple read-only endpoint with 2 parameters and an output schema that presumably describes the base64 PDF. The description covers the essential purpose and return format, the annotations cover safety, and the schema covers parameters and output. Nothing needed for correct invocation is missing.

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 input schema already documents 'fax_id' and 'user_id' (including the default for 'user_id'). The description adds nothing about parameters, but this is fine because the schema fully captures meaning. Baseline 3 is therefore correct.

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 a specific verb ('Retrieve'), a specific resource ('fax confirmation report'), and adds the format '(PDF)'. It is immediately distinguishable from siblings like get-fax and get-fax-thumbnail because it fixes the confirmation report document rather than fax metadata or a preview image.

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 context is clear: this tool must be called when a fax confirmation report PDF is needed. However, there is no explicit mention of when to prefer this over get-fax or get-fax-thumbnail. The sibling names are self-explanatory, but the description itself doesn't provide this guidance, so a small deduction is made relative to the highest standard.

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