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

The annotations already mark it read-only and non-destructive, so the safety profile is known. The description adds useful behavioral context beyond the annotations: the 25 MB rejection limit, the returned fields (file_name, mime_type, size, base64 data), and the set of accepted attachment types. No potential contradiction.

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 succinct sentences with the core action and source first, followed by the return value and limit. No fluff or redundant explanation; every clause contributes either to what you get or what breaks the call.

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?

With a single parameter and no output schema, the description is fairly complete: it states the URL source, the allowed content types, the return fields, and the file size constraint. The only minor gap is that the host restriction is left to the schema, but since the schema is structured and present, the description closes most of what an honest tool would need to be called correctly.

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 already gives 100% coverage by describing the url parameter as an absolute URL from another tool's response, restricted to the 100Hires API host. The description's phrase 'by the url another tool returned' simply repeats that without adding extra detail, so it does not bring value over the structured schema.

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 action—download an attachment—and clearly identifies the resource: attachments like resumes, candidate/application files, mail attachments, or call recordings. It also distinguishes itself from getters and uploads by pointing out it consumes a URL returned by another tool, which makes its purpose unambiguous.

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 tells exactly when to use it: when you have a URL from another tool that you want to download as file data. It does not name a sibling alternative or state when not to use it, but the input condition is specific enough to make the call context clear, so only the exclusion/alternative mention is missing.

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