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

Annotations cover the safety profile (readOnlyHint=false, openWorldHint=true, destructiveHint=false), and the description adds real behavioral detail: which types are rejected, the size cap, and a side effect (attaching an import note to a contact). It stops short of describing failure modes or what the returned asset looks like, but the output schema covers returns.

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 dense sentences with zero filler, and the primary action and destination are front-loaded ahead of the constraint list.

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 annotations and an output schema present, the description covers the key decision inputs (allowed types, size limit) and the optional side effect. Only deeper edge-case behavior (e.g., what happens on fetch failure) is unaddressed.

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 coverage is 100%, so all three parameters are already documented. The description adds only marginal meaning for contact_id by explaining the note's content ('that the file was imported for them'); name and url semantics are left to the 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?

States a specific verb ('Download a remote file') plus the destination ('workspace Media Assets library'), making the effect unambiguous. No sibling tool overlaps this import capability, so differentiation is implicitly clean.

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?

Gives concrete applicability constraints — public https only, allowed MIME types, 10 MB cap, and the optional contact-note attachment. It doesn't name an alternative tool, but no sibling does this operation, so the guidance is close to complete.

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